Theres been quite a few having this problem with there AFBs, they've been putting the stiffest step up springs in them & it seems to be the cure, but you'll have to get the calibration strip kit, it comes with step springs, jets, M. rods etc., but it will set you back like 55.00, on the AFBs & AVS, the primary jets are larger then the back because of the m. rods, i would put the stock jets & rods back in, then try the stiffest springs for the m. rods.