hey guys I have a 98 z28. Not heavily modified yet but working up to it. The issue I’m having is that I recently did an intake, throttle body, and fuel rail swap and now I can’t seem to get the car right. It will idle but cold starts it will run around 1200 for maybe 7 seconds then immediately drop to the desired idle. All my shift points seem off and it’s hitting 4th gear at 45. It will also cruise at 30mph without touching the accelerator but idle returns to normal upon stopping. I’ve adjusted the tps and blade opening over and over. Reset the tps and iac and have unplugged the battery as well. I’m at a loss. The car has been tuned before I swapped parts and was running fine.

went with the BBK. 92mm. I have HP but I’ve not used it yet and I’ve been digging around the internet trying to find any articles on tweaking the tune for the TB and intake

Also I used the new tps but not the iac. Tried swapping out with the old tps and couldn’t get near the desired voltage even after elongating the holes. Right now I sitting around .56 idle and right at 4.00 at WOT. Blade is cracked open around 4% I believe. I did 2% then reset but couldn’t achieve 100% throttle so I bumped it up another 2%

Managed to find a post on here that says with an a4 car I need to increase my shift pressures on the low side because the car is getting more air and the computer doesn’t recognize this so it’s not commanding higher pressures in low gears. Opinions?

Once you change out the stock 78mm tB for a ported or larger TB you completely fubar the ECM idle airflow tables. They now have to be tuned as the airflow entering the intake is a lot more at less throttle opening.

Basically your going to have to open the HPT and get on with it. I’ve never had much luck with idle tuning as it requires some clever formulas etc. you’ll have better luck asking in the tuning section.