You have to richen up your idle mixture screws. If you back out each one exactly 1/2 a turn it may solve the problem. I have KhromeWerks on mine and I had to go up one size on each pilot jet plus back out the mixture screws 3/8 a turn. I first tried 1/2 a turn with stock pilots and it got rid of about 75% of the popping. Didn't want to back out the screws any more so thats why a went with bigger pilot jets. Every muffler is different, so I would try backing out the mixture screws 1/4 turn first. If you still get popping try 1/2 a turn. You may get lucky.