1988 low power

Hi, I just got this truck a month or so ago, and it is a manual 4X4 V6. When driving another manual, I can floor it in 4th gear and get more power, but in my truck if I floor it in 4th gear, it seems to go, but just so weak. When I let off the peddle a bit, there is a certain point where it gets the most power. Could this be a bad fuel mixture, ignition coil, fuel injector (throttle body injected), or is this normal behavior for this 1988 nissan d21 v6 4x4?

read the codes first..

next compare milage against timing belt specs.

consider a proper tune up.

i did hear of the catalytic converter being bad. It does sound like the exhaust is coming out of a hole in the manifold gasket. I'll take it to checker tomorrow and get the codes.