1 Lucky Texan

P0420 is almost never the cat (though of course, cats can go bad, expecially if there has been some abuse previously like chronic misfiring) good to get everything else checked and sorted before blaming the cat. live data may help a lot here.

CEL on? maybe scan for pending codes anyway

what's the diameter of the UEL header exit? I'm no expert, but I have read that dia. changes along the exhaust are bad - you get weird nodes and uneven flow. You want the same dia. all the way thru I think. I love the Stromung twin tip on my WRX FWIW.

I think clogged PCV valves/hose can increase likelihood of some seal leaks.

is there any oil on the plug wire boots? might have leaky valve cover gaskets.

^^^^ that plus, any change in sound with brake use?

hmmm....maybe check the axle nut?

gasket? aren't these on with RTV or similar?

look at youtube for a video or 2? it's pretty easy but, some folks have messed-up the tensioner.... if you can drive something else for a few days, have a local rebuilder fix your OEM alternator, or consider replacing it with a used OEM (car-part.com) or check into a DBW unit or one from https://www.maniacelectricmotors.com/real.html typical units from VatoZone or similar are not well respected and can have short lifespans.

There were older models with CVT too - but I think it required modern fluids and sophisticated electronics to be able to transfer 'significant' power in a unit small and light enough, and with decent reliability, for a motor vehicle. I think the first Justy's were CVT. Using the van Doorne trans? those had less force on them than modern cars I suppose. CVTt has a fairly long history. Benz may have had a European patent in 1886, got a US patent in 1935. Some early motorcycles had stepless trans. Volvo had them , Audi, etc. There may also be systems that use variable volume hydraulic pumps and 'nutating cones' , toroidal systems, planetary gears??? etc. I guess they all have their own set of issues.....

car-part.com , maybe LKQ , their systems already have it figured out and should only show compatible parts. but, if you are shopping craigslist or a pull-a-part yard, take Ido's advice above. There 'may' be a thread at NASIOC with a list of compatible vehicles. I think there were some minor improvements internally on some(?) 2006 and later 5spds if you can find one that's compatible.

car-part.com will list compatible trans for your car.

vector - do you have grinding noises or just failure to go into gear? does reverse work? these other guys here are excellent mechs, but not being with the car, you need to shre exactly what's going on. if you do decide to swap, you MUST get a trans with the same final drive ratio. There could also be an issue with how the clutch is operated I think?

awesome, be glad to start reading your posts!

7. check bulb SOCKETS for corrosion inside at the bottom 8. put the hatch up and see if you have the same problem(wires might be abraded/shorting in the hatch boot)

does the auto HVAC system use that number? my WRX is consistently 7 degrees low, dunno where the sensor is, only found the one on the Outback which seems accurate.

you could easily have more than on issue and knock sensors are frequently bad on older soobs. also, cheap ebay knock sensors seem to work fine for people, easy swap too.

1157 type bulbs sometimes have shorted filaments. they are dual fil. and one can sag and touch - weirdness can happen.

when the dash lights are tested when the key goes to ON, does the batt light illuminate?

ah - good ID on that from a pro. guess it's small enough to get washed down a passage into the pan?

there are spring washers shaped like that, wavy-ish dunno why it would be in an oil pan unless, at some time past, the drain plug was lain on the ground or a bench and that stuck to it and the plug was inserted with that on it unobserved.

varies with region,in some areas, maybe Subarus are on the most-stolen list...I dunno in Texas, trucks are near the top of most lists; 1 - 2006 Ford F-150 crew cab 2 - 2005 Chevrolet Silverado 1500 crew cab 3 - 2004 Dodge 1500 crew cab 4 - 1996 Honda Accord 5 - 2000 Honda Civic

you might consider finding a local rebuilder to go through your alt. if it's bad. Might take a few days but, you'd have a better unit than typical rebuilts. or, get a used one from car-part.com .

I know you confirmed it, but, but, what about a triple check for slipped timing - do a tooth count to be certain? 'backfire' thru TB seems odd, but not surprising with starter fluids.....? if you decide to drop the ex. mani., look for 'dropped' valve guides too.

hmmmm....early DBWs sometimes had wonky pedal assemblies....... and, they have a 'zero' position routine too IIRC?