Rough Running and Idle

1997 F-150, 4.2L, 120,000+. I have a similar problem as some of the other posts. After truck warms up, idle still seems high and truck runs rough at all speeds and idle. Feels rough during acceleration. Sometimes when shifting from 1st to 2nd and from 2nd to 3rd, engine surges for 2-3 seconds after backing off accelerator. When stopped at intersection, sometimes engine will idle high and sometimes will drop down to near normal. I've replaced plugs and will replace wires today. O2 sensors were replaced six months ago. Checked EGR valve and found no blockage. Pulled IAC and it looks OK, no blockage. After replacing plug wires, I'll check the spark at the coil. The TPS is attached with two Phillips screws that are EXTREMELY tight and I could not get them off to check the sensor. How can I get the TPS off without damaging it, or should I just try to drill the screws out and replace them and the TPS? Can I spray throttle cleaner in the IAC and brush it out with a small toothbrush? It doesn't seem that dirty, but maybe there's something in there that I can't see. Anything else I should check/replace?

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