99.99% of idle issues after porting are caused by this. You must make SURE that the throttle closes all of the way. With the black plastic TPS housing removed, make sure the gear bottoms all the way out on the throttle stop. Also, hold the TB up to a light and make sure there is no light showing around the edges of the blade in the fully closed position.

I've NEVER had to tune the idle on one of my ported throttle bodies on any car I've ever had. That's not to say I've never had an idle issue, it's just that all of the idle issues have been physically solved, not by messing with the tune.

 

You can't just port it. You have to polish that turd too.

 

I had to modify the throttle stop in mine after porting so that it closed a lil more after P&P and knife edging the butterfly. It would go into reduced power mode until I'd did this. Now it runs so smooth and comes into power smoother. 08 5.3