The car is a 98 E0 with KKM, Pro-M 77, BAT pipe, 65MM TB, and Borla Cat-back.
I recently swapped out my lower, I wanted to see if the clean lower (no bars or plates) would run better with the Pro-M 77 and 65MM throttle body.
Before the lower was changed the vacuum gauge would read 18-20 in under normal cruising (50mph in 5th).
Side note: The vacuum easily drops off to 0 with the 65 and at part throttle the fuel air will read all green (not pegged).
So I change the lower and go for a drive after the idle settled out. At first things were fine, just a little slugish down low and real smooth acceleration.
But after a few WOT pulls the hesitation started again. This time I had the luxury of seeing what the vacuum and fuel were reading. Vacuum dropped to 10-12in, fuel pressure went up to 50psi, but the fuel air was reading normally.
I thought I had a leak, checked everything, but still was missing vacuum. Today I reset the computer and guess what returned, yep the vacuum is back to 18-20in and she runs smooth again, but only for a short time, then returned to 10-12in vac.
What does the ECU control that effects vacuum?
