Good luck wit it Carl, Do as the pro's have said, but also check the mounting of the fuel rail, I had the same prob a while back & it turned out to be the thread in the plenium that holds the rail on had gone so the pressure of the injectors etc was pushin the rail out, was no signs of leaks or anything & only happened when flat out !!

Karl did the MAP for mine in the same way as you want (Phil's old engine) & when we put Chip's Wideband on it, the fueling was SPOT on !! so trust his word, it WON'T be the MAP !!

jb