Ok guys long time lurker first time poster here with a problem that has been driving me crazy for months now. Here's some info about the car, what it's doing and what's been done so far, any help is really appreciated.

Car is a 2000 wrx gc8, it had a 2.5 / 2.0 litre Frankenstein that broke and now I have swapped in an import EJ20. Car has front mount, Vf34, eboost2, 4.44 box and a few other things, only thing I'm 100% unsure of is fuel pump and injector size (been told jecs 550) fuel pump will be changed to walbro soon.

Now, after the new engine has been installed and tuned (making 170kw on 17psi) it threw a check engine light under half throttle, and has since done it at different points of driving, e.g heavy load, half throttle etc etc. It's broken down on me a few times under heavy load and to get the car started I released a fuel line from the filter, put it back on and presto, it drove again. Now the only consistency is that when I drive for 15 minutes or so, leave the car in the carpark for 10 minutes, then start it, it will throw the code, which will eventually got away. It doesn't throw it much under driving anymore, but always after it has been parked.

I have changed, maf sensor, pressure sensor, air flow sensor, o2 sensor, re routed air hose, cleared fault codes, turned my bov into pull reserc, and have had it sent to many mechanics who can't figure it out. Again and help / advice would be appreciated, I can leave more info if you need it. Thanks

Also, the ecu is a unichip

Maybe I skimmed over it, but what code is the ECU throwing??

There is a thread here on how to check codes on a 2000 GC8, in short, connect two black plugs together under/behind drivers side of dash, switch key to ON (do not start) and count the CHECK ENGINE light flashes. Switch off and unplug two black connectors.

Long flashes are 10's
Short flashes are 1's

Flaaaaaash Flaaaaaash is 20
flash flash flash flash is 4

That would be code 24, as an example.

I had similar problems when I ran a unichip on my GC8, I fixed it by throwing the unichip away. Not being funny, it was just crap.

__________________
Air is for pussies.

Yeah iv tested the codes myself a few times and it throws 45 - pressure sensor solenoid, which has been replaced. When mechanic put the scan tool on it threw 45 and air flow sensor, which has also been changed. Forgot to mention above when the cel code comes on, if you drive it on boost, or over say 3000rpm, it seems to fuel / boost cut and violently bunny hop the car

Would love to delete the unifail, but can't afford another ecu and tuning, so need to deal with it as is unfortunately

How much boost is it running with the EBoost2?

Has 2 settings, 1 at 15psi another with 17. Same thing happens regardless of which setting it's on. has happened without making even close to over boost shutdown