silverton

I put GR-2's and H&R sport springs on my 2001, absolutely love the ride and the look.

AFAIK, the TCM is not flashable. You may want to look into an upgraded valve body if available it may help. Your tuned ECM is giving the untuned TCM inputs it's not expecting and is doing its best to make it work. An unfortunate byproduct of tuning and upgrading an automatic, if you google you'll find it's not just you. If you put your car back on a stock tune does the transmission behave normally? If it still acts up then it's not the tune and you have another issue. I turbocharged my 2001 GC-RS with an auto. If I wanted to drive it spiritedly I had to shift manually, otherwise it was already in third/"fourth" gear by the time we were across a normal sized intersection, acted like a CVT.

Way back before my GC was turbocharged I went out and played in the twisties with someone who had a GC with an ez30 swap. My car was auto, his manual, and he claimed he had a difficult time keeping up with me in some sections, even having more power. Knowing how to drive and to use your car efficiently has a lot to do with it. It's a shame you can't go out and play like this anymore, way too many people.

If you wanna go fast you need more cylinders

Monroe makes quick struts, rockauto specifies they're for the L model but that will only MAYBE be a slight change in dampening or spring rate. At anyrate, they will be tons better than your assumed 250k originals.

Resetting the TCM puts it back to default values. It's receiving inputs from the ECM it's not expecting so it starts to adjust for those funny inputs and now here we are. Are you tuned?

Without someone being able to reflash the TCM you're kinda stuck with what you have. It may even be an adjustment the driver must make for the car, instead of WOT... try like... 90%.

Remove the center console and follow those wires!

I hear you there buddy, I get to about 50% throttle with mine and I'm like "oh shit we're gonna need to slow down" lmao. That being said the car is rarely over 2500 rpm, it just doesn't need to be. Last night I was in a hurry to get somewhere and I may have experienced the 'hunt' OP is talking about. The car 'shifted' three times in a short period of time with the same throttle input, i just thought... 'why??'

You can have TSB's done whenever you want, if you know about them, they do cost money. Not like a recall that's generally covered for free if you do it within a time limit.

Has the car been in any kind of incident with the rear? I know there are some thin metal shield type things around/inside the rear bumper.

are you positive it's on the exterior of the vehicle? It's amazing the amount of rattle complaints I get and the car is just filled with all sorts of goodies that rattle in the cargo area. 'rec customer remove personal belongings' for due diligence make sure the spare tire holder is tight.

definitely red

I hate driving a manual in traffic, actually hate driving a manual period but especially in traffic, and that seems to be 90%-100% of my driving. I may be an outlier but Eye Sight does most of the driving and I'm fine with that, helps make it feel like I didn't spend an hour in bumper to bumper.

that's rod knock.

I was at the dealer a few years after the new CVT equipped WRX came out, and I had heard our cars did the neat CVT thing at that time. Pin it and it stays at peak RPM and the car just scoots, but too many people complained about it apparently and wanted shifts. Curious if anyone with a 15/16 CVT WRX can confirm that or not. Sometimes my 3.6 feels weird, but I think that's the fact the torque converter stays locked in like 90% of situations.

It could be the motor going out, or it could be a leaf or some debris in there.

Subaru and seeping/leaking rear struts, name a more iconic duo I think there is even a TSB for the Impreza model, that's where I see it the most.

Modify your upper radiator hose and you can use something like this https://prosportgauges.com/products/water-temp-sender-radiator-hose-adaptor

Can you take a video of what its doing?

They're also still using the same general suspension setup from 1993. Subaru is incredibly slow at adopting new things.

There's even a scantool break-in procedure. The manual is the same for the H4 and H6. These variable compressors are for fuel savings, not cost, for their overall EPA rating. Much like FB's can and should be using 5w30 but to meet their rated MPG you must use water.

If your voltage dropped low enough the modules aren't happy so when it was going around checking on the modules the RAB module may have been near last in line and didn't have enough voltage to say 'hey i'm here', so it coded until a couple key cycles with proper voltage. Often times when these persist you can fix it by doing a 'cap discharge' touching the neg terminal to the pos for a few seconds.

make sure the slide pins are lubed up!

The BIU is where all your fuses go on the inside, usually an access panel just in front of the left knee while seated in the driver position will let you look at it and replace any fuses that happen to blow. As far as parts availability I can not speak on that, but I do know somewhat recently there was a microchip shortage an whatnot so that's going to cause a big backlog for everyone, not just Subaru.