truck begins to backfire over 3000rpm?

[BrutonLS1]

I've got a 5.3 bored to 5.7. I converted it to carburetion and I'm using the edelbrock performer rpm intake, with a 650 thunder series edelbrock carb. It's got the edelbrock/msd Ls1 timing control module with the 6 different timing pills. I've tried all the pills, and the backfiring still happens? When I'm parked the engine runs just fine, I can hit 5500 rpms no problem, but when I'm driving and get around 3000 rpms to go faster, "pop...pop...pop pop pop!!" I'm not sure what's going on here guys? How can I adjust the carb differently? or what else can I do? Thanks in advance