94 toyota bogs out, idles really low

[krazy495]

What's up people, I have a 94 toyota pick-up 22re motor, 4x4, stick. For about a month now my truck has been bogging out and idling really low to the point that it wants to stall out. For all the people that know about these trucks they idle at 1000 rpms, the truck now idles at 500. Long story short,took it to my mechanic and this is what WE did. Replaced the the fuel filter, O2 sensors,mass air fuel sensor,spark plugs and wires, distributor cap and rotor,the computer system,battery,alternator(needed a new one anyway). Also took the motor apart checked the injectors,replaced 1 fuel line, check and recheck all fuel lines including the returns and the fuel pump, PCV valve and all vacum hoses. 5 mechanics and the toyota dealer don't know why or what is causing this to happen. I asked an old timer and he is going to swing by to take a look at it for me next week. But, ANYONE HAVE ANY IDEAS?
All help is very much appreciated.. thanks people.