3.0 idling rough

hello 94 ranger 3.0 , 5 speed manual, my problem is this engine idles rough, there are no codes, changed wires, plugs, fuel filter, ran injection cleaner through system, cleaned MAF sensor, changed air filter, cahnged every possible thing i can think of, have high pitched whistle noise, when idling, and cannot find a vacuum leak anywhere, can anyone help , thanks

Go to www.fordranger.com those guys have all the answers.

it may be the throttle position sensor (TPS) - it may be a little pricy though, so if you buy one, save the recipt just in case...