Originally Posted by
JamesLinder
If you look at the LS1 and LS6 their will only be a slight difference in the IAC curves in the slightly off idle position. The IAC
curve is specific to the IAC motor and plunger. A large high quality TB will come with a pre-drilled hole that is the correct
size so that the OEM IAC curve works as intended. I have played around with a half dozen throttle bodies, and yes if you
buy the lower quality ones, regardless of how much you pay, they will not work well with the OEM IAC curve because they
are not made properly. Talk to expert Dan Maslic, he will tell you that the IAC curve should not have to be altered unless
you should go with a IAC motor/plunger other than OEM, which I am not aware exists anyway. If your TB manufacturer
provided you with a new IAC curve for "their" throttle body, please post the specifics because I do not think you know
what you're talking about. Tuning idle VEs and idle MAF are tricky because the exhaust flow rate through the headers
at this state is minimal, not enough to keep the sensor as hot as optimal and with large camshafts are subject to reversion.
If you do not get the idle VEs and MAF correct, what is typically a rich tune at idle will behave a little better if you modify
the IAC curve, however this is not the correct way to fix the rich idle condition.