Howdy,

At freeway speeds going up a grade, the RPMs in my '97 SE (118K mi.) fluctuate 500 - 700 RPM. No problem on the flats. This issue has been irking me for months. I started with the cheapest parts first, and have replaced just the plugs and wires so far.
A lot of recent work done: trans has been gone through, new alternator, water pump, hoses, thermostat, tensioner, belt, A/C compressor, condensor, upper intake manifold, and the fuel valve that is on the top front of the motor. No engine light.

Any ideas?

You need to get a scan tool on the car if you haven't. Not all codes will throw a check engine light.