help my car

I have recently aquired a 86 rx7 gxl and i have had a dreadful time getting it to run again! before i even fired the engine i replaced the fuel pump, water pump, rewired some of the engine(due to destruction from rats) flushed the cooling system and gas tank, and adjusted the idle. now that i have got it running it will idle okay but wont accelerate past 3800rpms. when i try it will hesitate and cut out like it isnt getting enough fuel.i heard it might be the secondary injectors and possibly the ground connection, or the fuel pressure is too but that seems not to be the case because once it passes 4200rpms it drives fine. what do i do to fix it. it is irritating trying to drive it trying to avoid the 3800rpm range please help! this is my daily driver. 
                                                                     Scott

Sounds like the infamous 3800rpm hesitation. On 86 models you can run a ground from the map sensor to the thermostat housing. I am nu sure as to which wire on the map sensor exactly, but if you search some other Forums you may find a write-up on it.