1 Lucky Texan

^^^ good post seems like there have been some bad knock sensors recently too - bad running/hesitation/power loss when that goes bad.

weird can you post any pictures of what you're seeing? maybe start pulling breather, PCV, throttlebody and other lines and look for coolant/oil contamination. Is there signs of coolant in the IC? Also, compare all 4 plugs to each other. maybe the guilty cylinder's plug will look different. Once you feel confident it must be a head gasket - you know what needs to be done. Ivan's post #7 seems likely. The oil return passages have lower pressure so, oil getting in coolant might not happen. Just coolant into oil.

There's a huge thread at NASIOC dealing with "Scotty's cocktail" to help with synchro problems. It won't repair a car, but may reduce some of the clashing. Most people say stay away from synthetic, but Redline Shockproof may be an exception due to the odd formulation. I'd say, just try some fresh, name-brand but not expensive, NON-synthetic GL-5. If that doesn't help, maybe investigate the cocktail?

life is too short to spend a 'lot' of time trying to create a working 250K mile engine from a bad one. Either quick-turn it and stick it into some non-critical project vehicle, or get a better 'base' to work with. my 2cents

1/4, 3/8 and 1/2" ratcheting thumbwheels. Didn't use the the 1/2" but the set was cheap. Not 'necessary' but it gives you one more option for spinning the plugs in/out. I think some newer-style ratchet handles have a knurled/serrated thumbwheel - but my old handles don't.

I used the method mentioned by John, 2 different sockets, one without rubber/magnet insert. I also found these useful - especially on my H6;

seriously, actually look at the engine while idling and a helper puts it in drive, then in neutral. The load on the engine will change a little with the torque converter but, again, there are plenty of complaints that the vibration is NOT from the engine missing - it's from bad axles.

$60 is much less than what I was finding before my project. maybe 03 H6 is higher? anyway - unless you have some performance goal in mind, or absolutely MUST save the last dollar, get the OEM units. Even worth borrowing $$ from a parent or - gulp - ex-wife.

wait - if you slip the car into neutral at a light, does the vibration stop? This is often a symptom of poorly rebuilt front half-axles. I haven't read any reports of it being 'cyclical' though i suppose it's possible. Has the transmission fluid been changed on schedule? How does it look?

looks like ther's a dozen videos on Youtube for Subaru plug changes,watching 4-5 of them might get you prepared pretty well for the adventure.

any CEL codes? possible engine temp sensor or knock sensor problem. Most other issues might set a code.

96 might need new wires. OEM preferred. Aftermarket is dicey - maybe NGK or Denso specific for Subaru OK? maybe some dielectric grease to coat the inside of the boots. NGK or dealer supplied plugs SHOULD be pre-gapped. I'd check them to be sure though. If you get platinum or Iridium - be extremely careful as the iridium tip is easily damaged with gapping tools. different length/size extensions. I've read of some folks using a length of tubing to help start plugs but, The 2 DOHC cars I swapped plugs on felt confident as for starting the plugs. Widely different opinions on use of ant-seize or oil on the plug threads - your call.

When mine start having a problem, I'm buying stockers to go back on.

I don't have great answers to your questions. No squeaking yet on ours. I don't think a zerk could get new grease where it needs to go. The grease they furnished was very thick and I used it all. YMMV others here I'm sure have more experience with poly bushings.

there are numbers for the entire unit. there's a lef and a right side. The torque values are huge and, with stuff just 'snug', you are gonna want to drop the car and bounce it, crawl under with it on the ground and torque it to full-tight. Then , drive it around for a few days, re-torque again. Wouldn't hurt have it aligned - or wait till you get new tires and align it. while I went with poly, there's a DIY around here somewhere for the lca. Yeah, you might look here for some idea of what's involved; http://www.subaruoutback.org/forums/99-do-yourself-illustrated-guides/48910-lower-control-arm-rear-bushing-transverse-link-replaced-prothane-03-outback.html

that LCA rear bushing 'transverse link' is THE single most heavily loaded spot that transfers tractive and braking forces to the body of the car. You may wear-out tires faster too. To do it right is a little pricey. Do it cheaply (with poly bushings) and you have quite a bit more 'fiddly' labor and will also have a lot more harshness. If you put the car on jackstands and push pull the rear of the lca, does it hit the inside of the mount? if the fluid is leaked out, they still sorta work OK, but if rubber is gone - I could DEFINITELY understand them making noise. agree with GG on axles. And often, people go weeks/months with them making noise - but they will fail eventually leaving you stranded. Outer joints usually 'click' though - dunno about knocking. as for any other ideas to check; broken springs can be hard to spot, double check anti-sway bar endlinks and mounts (and for breakage), I guess struts/strut mounts could be a source???

maybe a clogged jet pump?

well, as for just working with some WAGs, I'll offer a couple; double check the 'transverse link' bushing. Sometimes called the front lower control arm rear bushing. as a wild experiment, you could swap axles left to right in the front. If the inner tripod joint is making the noise, it will make it on the other side now - or possibly stop with almost new wear surfaces in play (cause, only reverse would previously be wearing the axle.)

how many miles on the car? is it due for a timing belt? could have slipped timing by a tooth. I know you said you could not find a vacuum leak - but you might try using a vacuum gauge to see what it looks like when it stumbles at idle. I wouldn't discount the possibility of a bad knock sensor either since you have low power.

how many miles? have you done a throttlebody cleaning? There's a spray Seafoam with a special nozzle that will clean the throttlebody ans help clean-out injectors/carbon in combustion chamber. or, try a can of seafoam or techron in a tank or 2 of gas. CEL on? what's the code?

if the turbo had a cracked housing or something? maybe coolant/oil could mix. not sure though.

maybe pressure test the cooling system while monitoring the oil drain? also, unless done in the recent past, car is overdue for timing belt.

if the crank was at the timing mark (not the triangle/arrow - never the arrow) then there's no way the valves can hit the pistons. But, if the arrow was at 12 or 6 o'clock, then you could have bent a coupla valves. A compression or leakdown test should confirm. look for any hoses that didn't get put back on or have slipped off. Especially the IACv one that goes underneath the intake.

are saying you feel confident this happened after your recent work on the car? I can only dream-up some way to misconnect some hoses near the throttlebody and intercooler/PCV valve area. seems unlikely

If you parked, and someone bounced the car up - down at each corner, would you hear anything? these kind of problems can be tricky.