Ok, 88COBRA, he needs a 255 which was discussed in another thread.
Just to be clear, you don't happen to have an underdrive pulley on your crank, do you? I know a guy that left it on and was wondering why he was not building boost.
Ok just to be sure, all piping and clamps are secure? Are the vacuum lines secure and no leaks? What is your vacuum at idle? How is your blow-off valve hooked up? Forgetting not to plug in the blow-off valve will definately cause that problem. ( mine fell out the other day on the freeway )