Engine Performance problem
1986 Toyota Pickup 4 cyl Four Wheel Drive Automatic 85k miles

I have owned this truck for 24 years and I have been trying to figure out how to fix this rough idle for about 15 of them. I have replaced spark plugs, plug wires, cap, rotor,air cleaner, adjusted timing and idle speed, the idle air bypass valve is clean, replaced o2 sensor, no vacuum leaks I can find around the intake manifold.

The rough idle only occurs when the transmissiion is in drive. In park or neutral idle is fine.

I have not cleaned the Mass Airflow sensor element.

Please help as the idle has really gotten bad over the years and I must do something about it soon

thanks,
jpaxon