Im start with im a certified automotive tech I have built this car my self and has been ruining perfect for over a year. I have an evo 8 built 2.3 with 272 cams, built head, fic1250, t3 6266, denso cop ignition. Car making 620hp 31psi e85 stock ecu.
So my issue started one night I launched car when I went to 2nd gear car started droping what sounds like 1 or more cylinders, car does not pop or back fire. When you are wot around 15-20lbs 4800ish the exhaust sound goes flat but still moving and still building boost but is obviously has great loss power. Now I have changed every sensor on the motor except crank sensor, tps,o2. Ive changed battary alternator cop and harness plugs br8es gapped .18 and as low as .010 no change.I pulled head put new mls gasket on, pistons look perfect valve lapped and head cut. No change compression 170 across leakdown was good. Ive also cut the engine harness open look for any bad wire. Im completely stumped for over 2 monthes now if any one has any ideas maybe im missimg something please shine in :/

 

Almost sounds like limp mode(which I doubt)? Have you ran evoscan or do a virtual pull?

 

Yes ive had tunner go back in and make changes to fueling and timing watch the logs when this is happening and doesnt show anything out the norm. No knock count fueling mid 11s

 

I agree with you, it sounds like the ecu is seeing one or more signals that happen at the same time that doesn't quite register so it throws the car into limp mode.

This used to happen on some of the 2g eclipse dsm's when putting a 2g head on a 6-bolt bottom end using the 1g cas and eliminated the 2g crank sensor. It would see a certain mph, air flow, and rpm it didn't like and go limp mode. It always came up as cylinder one random misfire.

The fix was to install a potentiometer to slightly alter readings from the barometric pressure sensor.

One thing people used to do is unplug the tps, I would lean towards checking the crank sensor.