Spitting and sputtering under boost?
 

I have done and S5 NA/TII conversion and everything is running very well at idle. I have removed the emmissions and done the routing (or at least I believe ) per Rotary Reserections instructions. It is idling fine, but when I start to put it under even mild boost, it starts spitting and sputtering and backfiring through the manifold. The caps that I placed on the intake manifold are blowing off. It seems to be building pressure in the manifold. What have I done wrong or what is wrong?