Its a bugger. You would think that with as many sensors and bell and whistles these cars have there could be a sensor to detect a vacuum leak, or at least throw some diagnosis help when your car is idling at 2kRPM which is obviously an issue approaching any stop light or traffic jam... I never got a check engine light either through all my high idle issues...
The TPS is located on the drivers side of the throttle body. directly opposite of your throttle cable cams. Its a simple part to replace with only a T20 torx screw. My assumption with this sensor is over the years of heat and grime under your engine the plastics degrade and cause friction on themselves. Also the years of throttling up and down create minute wearing on the keyed throttle plate shaft that goes into the TPS. This wear and tear can give minute false readings to your cars' computer thus creating idle issues and not throwing a CEL since the computer is still getting a valid reading from the TPS... Try my approach first, im curious.
If you go forward to replacing the FPR the only tools youll need are a 5mm allen, skinny hands and a cheater bar to get the allen next to the firewall. youll also need some c-pin pliars and about 1.5 hrs of your time. there is a good write up on this site. when you have the FPR in site check the vacuum line feeding to the FPR from the back of your intake manifold. That bendy line can get brittle and crack, your FPR wont function properly with a cracked vacuum line which can create a rough idle as well. But when this happens it typically gives a stalling issue instead of a idle issue... either way id rather replace the $1 vacuum line rather than a $50 FPR. but while youre there munus well install $50 worthe of peace of mind... Hopefully all the info helps the trouble shooting. Hit me back and see if unplugging the TPS sorts it out. if so, it will save you some time and money and headache!!!