Growling Noise on high idle
 

I have a 2000 f150 supercab that i just upgarded to Lightning. i purchased a wrecked 2001 lightning off of ridesafely.com and swapped everything ( i mean everything) from fuel tank to wiring harness to total re-end... so long story short. after i figured out the drop resistor thing she fired right up and runs good. Only thing that is a concern is when engine is cold or air is on, when it kicks up to a high idle there is a growling noise coming from air intake... if i kick it down it stops. I say it acts up only on high idle.. but it will make that growling noise when cruising slow. sounds kind of like something is not seating right meaning not holding the vacum right. i was reading in service manual something about make sure to notice return spring on throttle cables orentation when removing because it needs to be put back on like it was ( spring? i would think it would only go on 2 different ways and neither seem better than the other). Also they say something about superchargers bypass being installed with installation tool/gauge? it only has a little adjustment but o never know. Any help?

Probably a dirty IAC

have a new one on there, but does not mean that one is not bad... i will put old one on there and see...

Fixed!!! it was new IAC. well not really the IAC but the gasket Holes where smaller than the old ones. So it actually was sticking out in the air holes making a terrible humm at idle. Thanks