1996 Chevy 5.7 liter running rough at low and normal speeds. Idles fine. Diconnected the Mass air low sensor and had no affect. New plugs wires and cap. What next?

Have you changed plugs and plug wires lately. Sounds like misfire, possible ! Should also check fuel pressure , plugged fuel filter or weak fuel pump ! Mass air flow sensor dirty, or map sensor .What engine do you have and does yours have How to replace the spider injector on Cheyv motor 4 3 or 5 7 liter

Check fuel filter if ok check fuel pump pressure and supply/ approx. 1 liter in 30 sec.

If it idles up and down real high, its the throttle body sensor. If it's a low up and down idle and runs rough it is mass air flow meter. If you unplug the mass airflow meter and it will just low idle (no up & down) then the mass air flow meter is bad.

Air filter box cover lose and sucking to much air, check to see if cover installed correct. Also could be mass air flow sensor.

Uh, maybe the scanner is right!?

i want to give you the right answer but the only thing i think of is the mass air flow sensor.

Its probably a vacuum line problem or EVAP or possibly the Mass Air Flow Sensor. Make sure that is hooked up as well. Examine all lines to see if there is a rip or tear or anything loose

fuel pump is going out causing the truck to run lean and miss

Can you check fuel trims at idle and under load?
If fuel trim is high at low speed and load, look for a vacuum leak.
If fuel trim is high at high speed and loads, look for fuel volumn problem or restriction.
If fuel trim is high at all speeds and loads look for pcm input fault, maybe a maf sensor problem?
If fuel trim is negative low speed and load, look for fuel pressure regulator or injector leak. If fuel trim is negative at all speeds and loads check ect and iac.

If you have the spider fuel system, that system is noted for problems. key on engine off, 60--66 psi fuel pressure.

That RPM sounds a little low, did BMW comment?