88 Voyager hesitates while accelerating

:naughty: Hello everyone:

Recently my brand old 1988 Plymouth Voyager (V6 3.0 L Engine) started to hesitate while accelerating and maintaining a steady speed. This usually happens after 10 minutes of driving with the engine warm. The Tachometer shoots up and down. I step on the gas, but it doesn't kick in until the RPMs go down to 1000 or less. The idle speed is between 800/900 RPMs.

The first things I've changed are:

Spark plugs/cables (it was time to change them anyways)
Fuel filter (what I thought to be the problem, but wasn't)
Air filterNow I've changed:

Throttle Position Sensor (drove just fine for a lil' while, then hesitation came back again)Gonna change tomorrow:

Oxygen Sensor (I believe it's never been changed)
PCV valve (Should it always make a little rattle when the engine is on? or should it rattle and stop now and then?)I did the on, off, on, off, on ignition thing to check the codes and I get:

code 24 -Throttle Position sensor voltage low/high
code 36 - Wastegate control circuit open or shorted (turbo only)

If the TPS voltage is too low/high, what would cause/fix this problem?
What else could be causing the hesitation?

Thanks!...
Any feedback will be appreciated...:1zhelp: