2002 PF, with close to 53k miles. recently trouble with high rpms at low speed. Have to push accelerator up to and past 3500rpms just to get the PF to move, then runs at 35-40rpms at 65mph. O/D light flashes at start-up and SES light on (P1456 code). took it to dealer said throttle was out of limits, readjusted it (for lots of $) and SES off. Came back on about 2 weeks ago and it's getting worse. any suggestions?