Sadly, I don't think there is enough information here to make any suggestions.I assume that when you replaced the tank and pump you flushed the rest of the fuel system, replaced the filter, cleaned the injectors?Have you measured the fuel...
To answer your question - yes, the pump can overrun the stock regulator, and an aftermarket FPR is a good thing to have on a modified Evo 1.I would suggest a total service of the fuel system, though. Clean out all of the old fuel, clean the...