I have a CAI, HS header, and a Bomb exhaust muffler.

After I hit 3K rpm or higher, then release gas either to slow down or to shift gears, when the engine whines down to 2.5K rpm or so the muffler makes a pretty loud pop sound. Like air is being forced out all at once, in one big chunk or back firing.

What is the cause of this and how can I fix it????
Thanx for the help.

I believe this is called "after-lighting". It causes no harm to the car (unlike backfiring) but can sometimes just be annoying. If you install a fairly large resonator (20" or so) it should remove that popping with no problem.

so I should probably just go ahead with the custom cat-back I was quoted for! Wit the flowmaster resonator! But that would also make my exhaust louder, I have a bomb exhaust that thing is pretty loud with out the silencer.