Since I could not find a PI intake, I decided to replace all the vacuum lines and the O2 sensors just to see if it would help.
Replaced both pre-cat sensors and every vacuum line except the purge valve to charcoal canister line ( goes into fender well).
It actually helped a lot. In particular the purge solenoid to purge valve had a crack in it. Not a complete hole, but cracked to inner lining. After doing that, the car ran better, but not perfect.
Seems to have its power back mostly. Still idles very rough. Idle has a chug-chug quality to it. Car shakes at idle.
STFT numbers changed too:
After initial warm up (car idling):
STFT B1: -7% to 0%
STFT B2: -2.3% to 2.3%
After a long drive ( car idling):
STFT B1: -3.9% to 1.6%
STFT B2: -3.9% to 2.3
When put back in gear after idling after long drive, B1 goes lean to -7% but recovers to -3.1% to 3.1%
At highway speed both banks seem normal at -3.9 to 3.9%
Idle is still very rough however. Also exhaust sounds off. Car has a Flowmaster cat back. Doesn’t have the distinct Flowmaster sound. Sounds harsher and more percussive almost booming.
The vacuum line from the purge solenoid to the canister looks pretty rough so I am going to replace it this weekend. I might just teplace the purge valve, solenoid, canister, and lines while I’m in there.
Any suggestions on the very rough idle will help.