1 Lucky Texan

hmmmm....seems like I have read of the starter's commutator needing cleaning? quick search found this;

my first guess is, they may be reversed. Diodes are polarized. and, not really sure they can be used in alt. field excite circuit???? (hope someone smarter will respond)

except for the rpm weirdness, I'd suggest checking trans fluid level (while idling of course)..... maybe a vacuum gauge test? you can find info online of the old-school use and all the stuff it can find

Did the battery die or was used until completely discharged at any time? Or maybe the car was jump-started? possible the ECU has lost its 'zero calibration' from the throttle I guess. There is a zero re-learn procedure. maybe someone more familiar with the newer cars will respond.

just pointing out also, that due to MTs sharing lube with front diffs, fluid choice can matter in 'feel'/smooth-shifting. many folks experience clashing when using synthetic fluids. NON-synth, name brand lubes seem best. There is a Walmart semi-synth blend that some folks claim is a good value.

both NASIOC and utimatesubaru.org could be good sources too. be sure to search thoroughly and read at nasioc before asking questions - some guys over there are not 'noob-tolerant' .

if you could purchase from a supplier that has a free return policy - probably a local place? - buy both types, return the unused one.

Well, the cat conv is really aimed at reducing operational pollution. But, i agree with you otherwise. If the car is otherwise not leaking and is running well - better than the demand for a replacement to me. cradle-to-grave impact is often overlooked. But, ultimately, it may come down to the Laws of his State.

lol, if your concerned about minimizing your pollution 'footprint', why are you driving a 40 year-old vehicle?

many cars are money pits. Subarus have one or 2 design 'features' that can make them more expensive to maintain. Maybe someone could direct you to a different shop near Hermitage, with subaru-friendly mechanics. have them diagnose/'triage' the car; what must be done now, what you should save-up for, what you can live with(drips?, burned out dash lights? squeaks?) but yeah, maybe the car was abused by a previous owner and now those chickens are coming home to roost many people trying to keep older Subarus going fight; axles (rebooted used OEM are best value), headgaskets (worse on certain years, worse !f engine ever overheated), AWD issues, wheel bearings (easy for substandard parts to be used, easy for installation to be poor) did a previous owner run mismatched tires? very bad for the AWD, did they get confused about what fluid goes where? easy to get an abused Subaru, the more owners it's had, the more likely it was improperly maintained.

is the exhaust OK? seems like the cat may be loose!

Hmmmm.....if it IS cranking but not starting, here's a coupla things to try; spray some starting fluid into the intake to see if it fires - if so, some odd issue with fueling. measure the voltage while cranking, really should be 10 or more volts I think. are any codes stored? even pending codes?

nvrmd

denso starters can have worn contacts/plunger in the solenoid when old. Rebuild kits are available. or, iffy batt cables or ground connections???

H6 is super smooth running engine. Premium Fuel though..... often, codes do not really point to a part mentioned in their definition and can sometimes be fixed with attention to details like; wiring/connectors, vacuum hoses, proper sparkplugs, etc. This is where good diagnosis is helpful. Other than coils, plugs and valve cover gaskets - most everything else on that car is easy to get to.Of course, age and rust can be tricky to deal with.

if you whack the starter a few times with a piece of wood and it consistently starts better afterwards - you need to rebuild the solenoid. kits are available. maybe investigate the battery cables , they can be corroded under the insulation.

I assume it has a knock sensor? they can kill power and economy if bad.

if you do your own inspection, read-up about 'torque bind'

most of the threads 'stickied' (with the little pushpin symbol) at https://www.subaruoutback.org/forums/gen-2-2000-2004.110/ are the common issues. Of course, ANY 18 year-old car could have ANY problem you can imagine - easily 2-3 or more as well. shop carefully. also, in a new thread, ask for a shop recommendation near Spokane, have a conversation with a soob-friendly mechanic about doing a prepurchase inspection on any vehicle you are interested in buying. He might also have a customer ready to sell.

front or rear pass seat? Some newer models regularly do an evap pressure test. If it is clicking more than 3-4 times a day however, could be a failure of some sort. is the CEL on? maybe scan for codes.

do you have misfire codes? If you have 2 that are bank specific (P0301 and P0303 for example) you may have a cam sprocket that has slipped it's timing.

??? if this engine has a coil and PLUG wires, could easily be a bad coil-pack. Due to waste spark ignition design, a bad coil will kill 2 cylinders. 1&2 OR 3&4 .

Man, I dunno, is the expected gain in power gonna be more than the loss from the xtra mass you are adding? still, good looking installation.

are there useful or cross-referenceable (?) numbers on the installed part itself?

um, I wonder if your engine could have a plastic air/oil separater plate? They are on the rear of the engine and can be notorious for leaking.