Originally Posted by AirBrontosaurus
It could be a vacuum leak in something that is only opened at higher RPMs (EGR, maybe).
However, usually vacuum leaks have other symptoms, and a CEL would probably come on if your EGR isn't working.
Did it just start happening randomly or did it start after you added/deleted something?
No CEL. I recently put on lowering springs, changed my spark plugs, cleaned and re-oiled my K&N, cleaned my MAF and TB.
I dont see how that would cause anything like a vacuum leak.