Chevrolet Repair: bad idlie, torque converter, cat converter

Question
i have a 1994 chevy z71 it has bad idle and i have changed the tps sensor (that is the code the car lot got off the computer of the truck)i have change plugs wires,plugs, cap and rotor, air filter and fuel filter(had a little trash but not a lot. if im stopped and in drive rough idle and now when going down the road rough idle if in neutral or park it fine. if it helps its gas motor. im getting about 12-13 miles to the gallon. please help!

Answer
Hi David... check MAP sensor, check for a plugged cat converter, bad o2 sensor.just because they don't trip a code doesn't mean they can't be bad. plug in scan tool and look at the readings for each of those sensors, make sure they are in manuf range.try a good inj cleaner. also check to see if lock up for torque converter is disengauging. hope this helps