[MiracleMax]

Cutting off vacuum to the EGR and the FPR is what you have achieved, not the best choice in either case. Since A. your upping fuel pressure and B. your eliminating exhaust gas recirculation from the process.

The stock Ford fuel map is mapped out to include EGR function and a manifold pressure referenced FPR curve.

cutting off EGR function creates a lean condition when the car reads it as active (since there is more air present). However, the EGR is really only on at high speed part-throttle conditons (it cools combustion temps to inhibit the formation of oxides of nitrogen).

Now cutting off the reference to the FPR is the worst evil here, what you've done is somethign akin to a jedi mind #$%* on the computer which is now trying to frantically adjust the amount of fuel entering the combustion chamber based on what the O2 sensor is reporting (the MAF still thinks everything is hunky-dory and is telling the computer that X amount of air is entering the engine and the injectors should stay open Y amount of time to deliver S amount of fuel. Since the fuel pressure has shot through the roof, the injectors are firing a nice high (for the system) pressure finely atomized spray of fuel which coincidentaly is to much. by the time the combustion event has occured and all the availalbe fuel that can be burned with all the availalbe air is depleted leaving unburnt fuel (which can cool the combustion event BTW) goes out the exhaust and shots past the O2 sensor reading rich. Then on to the h-pipe and the air injection which provides more air to burn the unburnt fuel. Incidentally a rich fuel system will also cause the cats to run hot (made this mistake on an 86 IROC once and burned the carpet in the car). Due yourself a favor and give the computer a breakby opening up the line to the FPR again.

If your making insane power with the BS mod, then look to the fuel system for possible problems (under injected if your modified or low fuel pressure, or clogged injectors, or whatever.)