Hello,
When the RPMs are returning to idle, for brief moment, they hang right above idle (not noticeable all the time). I added an extra return spring to rule that out, but it didn't change anything. It has a Holley TB (and other mods) and it was Dynoed tuned (the tune is loaded with SCT X3). All the vacuum line and such look good. Do you think it is a problem with the IAC or tune?