1 Lucky Texan

you must look at the crank timing - ALL the marks must be on. Timing can slip with the belt OK. Crank timing AND cam timing must be correct - you have an interference engine. is this original timing gear? The toothed idler fails frequently when old - tensioner occasionally. Bad tensioner or idler can let the timing slip AND allow belt to slap around inside covers making racket. spark plug issue is weird......

did it overheat? is the radiator full (look in the rad) could be slipped timing and hitting some valves - how long since timing belt service? how loose was this loose plug???

I can 'almost' always tell when a battery is getting weak by the slighly slower-longer starts. A good parts store will have a load box or Midtronics device to test the battery in-car. of course, there can be issues with corroded terminals and cables - but a well-maintaned 06 may be too young for those issues to be severe. Same for the starter.(though, my 06 WRX's starter drags/'is slow to release the drive gear', in the cold - it still starts the car just fine)

yeah, if the terminals were tight and fairly corrosion free, you just need a rebuild kit installed for the contacts and maybe the plunger. Check ebay. If there WAS corrosion on the cables - that may have been the only problem. try not to use a hammer too vigorously - I think the magnets inside are brittle. better to just whack it with medium light force with a piece of wood. That is really not a longterm solution though, just to diagnose that the contacts are worn.

look for bubbles in the fluid while idling, have someone turn the wheel. you don't want bubbles.

if it is the ATF-HP stuff from Subaru, it could be red in color if still made by Idemitsu. (some say 2 different sources have made it so.....?) But, a fluid change is a good , DIY place to start. inexpensive compared to almost any other trans work. However, another concern might be whether someone has confused the front DIFF for the trans fill tube. It has happened before.

honestly, there may be 'diminishing returns' at altering your treatment of the car very much. Yeah, we can theorize about this or that change but, without sending fluids in to Blackstone or Polaris labs, examining plugs, throttle plate and maybe internals for deposits, etc. , hard to say exactly how to tweak the maintenance to optimize the lifespan of the car. A weekly/bi-weekly highway runas suggested above and not letting the car sit around for weeks with only 1/4 tank of gas might be the most 'practical' things you could do.

synthetic oil also keeps 'varnish' in solution better - expect your oil changes to look darker. I suppose if your spark plugs look normal, that may be an indicator that the low-use isn't building carbon on valves or elsewhere in the combustion chamber. recent guidelines on tires also discourage driving on old tires.

could be a hole in the condenser, or leaky schrader valves too.

Short trips are considered 'severe duty' and can be as bad for cars, in different ways, as off-road use, racing, or overloading with cargo. Is the car ever used for longer trips? On weekends? First, the maintenance schedule has a TIME side and you should do maintenance according to it. (exceptions 'might' be things like air filters and sparkplugs - but even fluids degrade over time - plus, with low usage like you experience, they collect moisture from condensation) you should also consider re-fueling before the car indicates empty - maybe at the half-way mark. I see nothing wrong with you idling the car a little longer and/or using a block heater - you will get poorer mileage, but you 'may' be less likely to carbon foul the plugs and engine oil may be better able to 'boil-off' any moisture collecting in it. If it hasn''t been done, you are WAY overdue for a timing belt service too.

a rack from a wreck should be a decent bet - very rare to read about problems with soob steering racks.

I'm not clicking that.

^^^ yep, next time it fails, whack the starter with a piece of 2x4. could be intermittent solenoid contacts.

2009 ? it may be in the tank., or maybe that's Imprezas. is the check engine light on? even if not, the pats store can scan for pending codes.

try tapping on it while idling - some have reported there is a common poor connection inside MAFs of certain year models. If idle changes while tapping it, maybe that would confirm the problem?

ok, 60mph is about - what? 22 - 2500 rpm? have someone rev and hold the car to that rpm while looking for bubbles in the reservoir. maybe even gently push-pull on the hose? any work/service done to the PS before this began? topped-off with 'generic' ps fluid? Is the fluid still red or does it look like coffee? You could try getting some fresh ATF in there.

if so, or bent rim is still suspect, swap front and rear tires - see if problem is better/gone.

check inside the radiator - don't rely on 'just' the mark on the o'flow tank. system can be pressure-tested. might confirm the waterpump. or bypass hose w'ever. wonder what the code was that triggered the CEL? misfire still?

I would expect a bent rim would have been caught by tire mounting techs. And it's hard to figure how it would be 'notchy' feeling in the wheel. can you describe this feeling better? does the tracking of the car change? is it some that happens only 2-3 times when turning the wheel? something that feels woodpecker-like in its repetition? (several pulses in a a coupla inches?)

it's kinda all guesswork - pay more money for the potential of longer-life and better performance? you might also look at the top-line batteries at O'reillys. they are AGM made by East Penn/DEKA.

interference engine, risky on the 2.5 to not replace the rollers in the TB system. The toothed idler is 'especially' prone to failure. you could test the thermostat on the stove, if it opens and closes smoothly at 170* F, re-use it. There is a Stant Xacstat that is OEM-style that is not crazy expensive. spark plugs are a little easier if you're also doing the VC gaskets. clean and re-use the PCV valve?

you didn't mention alignment - maybe the tow or other parameter is a little out-of-spec? there is a 'cardan' (?) or type of u-joint on the steering shaft that might create odd feelings in the steering wheel. Dunno about only at speed though - weird. a very common problem is also air in the power steering fluid - often caused by a bad o-ring at the suction hose adapter on top of the PS pump. But, also not usually reported to be at speed only..... some people have had worn rack bushings create problems. odd

most newer style require a quick bake in the oven. I'm sure you can find DIY stuff and even youtube videos.

not sure , but, if only the seals are bad - a rebuild might be just fine? others will know more. if you don't like what you hear from S-Wings, checkout out RetroRoo in Henderson ; http://retroroo.com/ Shawn will take of you I'm sure!

possible Engine Temp Sensor - doesn't 'choke' the car in the mornings. But I'd expect hard starting/poor idling until warm. on an older car, could be some type of temp sensitive vacuum leak. a vacuum gauge is cheap to buy, maybe free to borrow from a parts-place. Check when cold in the morning, compare to warm conditions? maybe a sticky valve in the failing misfiring cylinder? carbon buildup or dropped guide?