Do I need a new TPS?

99XJ 4.0
I am experiencing lower RPM's at start-up, occasional studdering during acceleration and constant one at 70+ mph.
I tested the TPS and measured voltages between 0.95 and 4.06. I am thinking I need a new one, just wanted to confirm.
Is this dealer only item, or I can purchase it from somewhere else?
Thanks
Boris

Personally I would remove the throttle body first, give it a good cleaning on the bench, remove the sensors before you go all cleaner happy though. Alot of those plastic sensors dont like carb cleaner solvents and tend to melt. First off though I would run a can of decarbonizing cleaner thru BG44, GM top engine cleaner, SeaFoam then remove and clean the throttle body. How long since you did a tune up ? I change my plugs and stuff every year and I commute on hiways at high speeds so I don't get all that much buildup in the motor itself but the TB does get dirty...

the other way to check the TPS is check the readings while u move the throttle from closed to full, works better if u have a non didgital meter.