RPM surge
 

When my 97 PS is in park or in gear it bounces around between 500 and 700 rpms. Sometimes it does it more when its in gear rather than in park. Any suggestions on what could be causing this?

Any modifications? How long has it done this? Start by pulling the codes.

It's got an intake and a straight piped exhaust not throwing any codes.

What's your fuel pressure at the FPR? Should be 40 - 80 PSI. If it's closer to 40 PSI, add a BB (for a BB gun, not a ball bearing) to the FPR to bring up the pressure.

My 97 f250 would surge when I was driving at any speed. I just found out yesterday from Ford that it is the sollenoid body.