My fb has a s4 top with a street ported fd engine setup on a t04e. When I had the fb top on, it would idle fine. But a little underpowered because of the small venturies of the throttle body. So I done a s4 top and now I have cold startup idle issues. If I gas it too fast, it backfires until it is warm enough to run on it own. There are no vacuum leaks. When the engine warms up, it idles fine at 1100. All the rats nest is gone. I'm thinking maybe I have not enough vacuum. The timing is set 15 degrees negative for boost. I have vacuum to the fuel regulator, boost gauge, waste gate, bov, and the oil filler vent. Any suggestions?