[USMC302]

It does sound like it could be a vacuum leak, but I would still try pulling codes and looking for any O2 sensor errors, if they went bad and are constantly reading rich, then the computer will try to ensure a lean condition is used while the TPS tries to compensate to keep the car running by increasing idle. Not all codes will trip the check engine light. Eitherway, the TPS should not be reading 5v, what wires are you connecting to to test and are you using a digital volt meter? Let us know.