[RPM427]

The FMU steps up the fuel pressure in a specific ratio. It supplies the extra fuel you will need under boost. You can also get a stand alone fuel system that will do that for you, without the FMU. That feeling above 4000 rpm is the engine not getting the fuel it needs under boost which almost always results in SEVERE ENGINE DAMAGE. It is like running nitrous wihtout any fuel inrichment. Your computer doesn't know your engine has a supercharger on it. If your supercharger put out more boost you would have burned pistons and posible catasropic engine failure. You may already have damaged your engine depending on how many runs under boost you have made.

PUT THE FMU BACK ON!! Get the 24lb calibration dics for it and make sure your MAF is calibrated for the 24lb injectors. Then your problems will go away.