If I read this right, are you using the FI fuel pump? If so, it pumps 35 to 45 lbs. of presure, Way to much for a carb. What you may be having is (and this is an EWAG) a fuel pump problem with fuel backing up at the pump and NO return line for the excess fuel, or a fuel starvation problem. If you are using a fuel pump designed for a carb, the proper fuel pressure should be around 7 psi. THe float bowls may look good at idle, but come up a little empty when driven or accelerating. Just fuel for thought.