What would cause the cruise control to weird out?

If I run it up to say 65 and hit set, it will accelerate to about 75, hang there for a while and s l o w l y ease back to 65. It will do it sometimes on resume also but not as bad. It will overshoot a few MPH and then drop back but again slow.

When I replaced the lift pump last week I disconnected the batteries and when I started it up, it idled at 2500 rpm.

I did the TPS recal and it idles now. Is there a cruise reset procedure too?

Kevin