Toyota Repair: 22rec, mass air sensor, air fuel mixture

Question
dear sir, my truck has been to multiple shops around here including toyota. ive been having idle, performance, and fuel mileage problems. truck has a new motor, mass air sensor,tpi,dist.,fuel press. reg.,o2 sensor,dist.,and egr valve. i just learned that the dash potshould have a filter which  has to be used to act with barometric pressure to work properly.altough when adjusting the idle speed screw on the dash pot there is no change in idle speed at all. by  replacing the filter  properly the truck runs great but i still have inconsistent idle, idle smooth at 1000rpm, next thing idle speed drops when warm and idles rough, very inconsistent. smooth idle when cold, when warm sometimes it idles smooth and then rough, idle speed changes as well. removed the throttle body today and cleaned extensively. put it back, runs better and smoother but still off, this truck used to idle so smooth it was hard to tell it was running. you can tell its running too rich,black exhaust and smell. any help would be greatly appreciated. thanks

Answer
I can suggest a couple of reasons for this, there could be a problem with the air flow meter,or the water temp sensor for the ECU, also make sure there is no air leak on the intake system anywhere and check the ground connections on the intake plenum chamber where the two pieces of the intake are connected together. The dashpot you mentioned has no effect on idle it is used to hold the throttle plate open a small amount when the engine is turned off, you can vary the idle speed by turning the screw on top of the throttle body but this will not affect the air-fuel mixture, which seems to be the problem.