WRX Misfire, Flashing check engine, Bucking, Hesitation

Hello all, I'm a new tuner, long time engine/vehicle builder. Ive got several Subaru's, ranging from a 96 Impreza Brighton with a ej205 swap, to an 07 Forester with a full STI swap. the car in question though is a 2003 Wrx, that had rod knock, and received an "ej206" or more like what I believe to be an EJ20G- because it is non avcs, and came with twin turbo headers from a Japanese legacy twin turbo 1998-2001.

The car runs great under about 8lbs of boost/50%throttle , and subsequent load, but above that, it sputters, bucks, wot on lower rpms will hesitate/bog down before bucking, sputtering, its a nasty feeling.

The car has Cattless headers, up-pipe, downpipe, strait to the back, turbo inlet, cold air- bone stock otherwise.

I've gotten very fed up looking for the cause, the internet sources for these motors has become so clogged up with misinformation, good information, and like problems, that I can't find any help.

Things I have done attempting to fix the issue-

Plugs, new, NGK Laser Iridium

fuel pump

intake manifold, through to the intake, gaskets and hose clamps- there are no leaks or wrong connections.

turbo waste gate, internal, stock

MAF, and MAP (new)

battery, and cables through to chassis grounds, alternator and starter.

My top ideas, that bring me to write this post to see if anyone conquers-

Would love to know if someone can definitively tell me if this "ej206" has higher compression, thus needing a significant ignition retard?

Coil packs, would all four really go out simultaneously?

Boost control leading to fuel cut... 3 port on the way- however I tried unplugging stock controller, and just routing compressor nipple to the waste gate, 14psi- to no change.

Would love a response on HP forums, would be a great place to see forums kick off but, I've never had any luck getting a response on forums period- worth a shot. Appreciate your time!

i would imagine the ecu will need tuning to suit this but data logging will be the best place to start

regards Ross

In the title you said the "check light"was flashing - first thing I'd do would be to see what the log for the ECU showed, the proceedure should be available on-line. Does it seem to be primarily a loar or an rpm issue - or both at different points?

I would also suggest taking a step back and having a good think over the fundamentals - what you are actually working with - fuel system, pump capacity - you've changed it but for what and is the wiring up to the draw, filter change (including in tank sock if used), spark plug gaps, etc.

Not an engine I'm familiar with, but the basics apply to all engines.

What is the full engine number and code, as found on the block?

Immediately went over the ignition system, plug gap is good, coils are good, fuel pump wiring I checked the resistance against Subaru’s Factory Service manual, and it was good, both off and priming.

I’ve got a couple data logs where I replicate the problem. (I’ll try to upload tomorrow when I’ve got my laptop handy)

It seems much more load caused, as I can pull to redline on 8lbs of boost, maintaining about 12-12.5, I never see afr’s change outside of limits when it cuts, it seems a lot like an over advance of ignition, but I can’t say that for sure because I tried a global timing adjustment retard of 2 degrees and did not get any better results.

wondering what else a higher compression ratio engine should need changed for a base map, this is just to make the car drivable 4-5 hours distance from me for dyno time and a full remap.

appreciate your help!