Rough, irregular RPM @ idle and low acceleration
Car: 2002 WRX
TXS TBE with Magnaflow HM cat in place of TXS cat for better emissions
Blouch 19T turbo
Perrin Intake (regular size MAF; got rid of "big" one)
Hallman Pro RX MBC (@~15-16 PSI)
Tuned for these mods to ~270 WHP/TQ
My car does not seem happy. My tuner says that at low throttle, the A/F ratio compensation is all over the board, totally erratic and unpredictable. If it wasn't so erratic, he'd be able to fix it. But due to the randomness, it's not fixable. He theorizes that it's a partially faulty ECU, and that I should get a new one, transfer the tune to it and see if that fixes it.
I am not sure if that issue is related or not, but my car is running weird at cruising speeds. When on a flat road and just coasting down at constant throttle, it is not smooth - it is jerky and annoying as hell. It's not scary like a car running out of gas, but it's not smooth like it should be. It is enough to make my head move an inch while driving. What could be causing this, and how do I fix it?
Also, the turbo doesn't spool up smoothly... at WOT it acts weird when I just floor it. When I am gently in flooring it it behaves a little better, but still, it's not what I'd call smooth, and it does occasionally hiccup quite badly at times (enough to break the car loose on anything but dry pavement).
This whole project is getting quite frustrating since I've put over $3000 into my car to get it working (swapped turbo, new muffler, custom-installed cat, replaced bad fuel tank, new injectors, MBC, tuning and labor). Oh, and LOTS of my very-hard-to-come-by spare time. I think the only thing left to replace is the car...
To add insult to injury, I failed emissions today for the third time. Both the last time and this time I was "assured" that it would pass just fine. I am roughly doubling emission requirements now, but that's another matter...