I am new here and have a 1984 D-100 shortbed fleetside with the leaning tower of power and a 4 speed manual A-833 transmission. I am having a problem with a SEVERE lean spot at about 1000-1500 rpms while under load. The truck wants to buck and jerk violently. I have replaced the carburetor, fuel filter, fuel pump, and adjusted timing, replaced distributor rotor button, cap, wires, and plugs. My electrical system is fine as well as the coil and ballast resistor. I am still using the old ECU that is hanging from the air filter, so it is controlling my spark advance since my distributor does not have a vacuum advance. My carburetor is a new Holley 1945 that seems to be fine, but is factory sealed for adjustment. Yes, the accelerator pump seems to be squirting fine also. I have replaced all vacuum lines and checked the intake manifold and carburetor base gasket for leaks. I just ran a compression check also, and all cylinders are around 125psi and within 8 % of one another. I just can't seem to fix this problem!!! Any tips on what to try???