To make a long story short, I bought a 98 GT that had a broken timing chain. I replaced the chains, guides, tensioners, and the driver's side head, (pi swap already done). I got everything put back together and everything seems fine, idles fine and compression is 110 across the board. The problem I am having is as soon as I hit boost, the car falls on it's face. It is almost like someone is hitting the brakes. It has also backfired a couple of time when doing this. I am baffled on what could be the cause. The setup is this: completely forged bottom end (8.5:1), PI heads, stock PI cams, Mac long tubes, 42 lb injectors, SCT Xcal2.