I noticed when I'm either in 1st or 5th gear boosting @ about 7-10psi, a little after I let off the accelerator the car backfire's pretty loud. Does this sound normal? Below, I've listed information about the car and what I have. Any help would be great.

S5 vert w/ TII conversion
Knight Sports Turbocharger
Knight Sports ECU
Knight Sports Dual Pulley System
HKS 3" downpipe
Straight Pipe

 

Normal.

 

thanks for the quick reply. one more thing, i noticed that each time it backfires differently?

 

There ya go. That's what's "causing" it. Nothing to be concerned about.

 

lolz, thought so. first time experiencing backfire! thanks alot

 

It makes a good light show for night time highway cruising. Purple flames

 

Mine are more blue-ish at the tip, turning to yellow about 6 inches to a foot away from the tip.