Engine jogs down to about 2500 PRM's

Lately I've noticed a problem with the engine whenever I hold the accelerator around 3000-3200rpm's. Regardless of the gear, but easily noticeable on the highway with the cruise. The engine will be keeping speed with 2300-2500RPM's (say 70mph). Demand increases on the engine (incline, resistance) so the cruise ramps it up a notch to 3000 or so. Engine jogs down to about 2500 and will continue this cycle until engine demands the 4000RPM's to make up for lost speed. Then it operates fine. It seems like its just that 3000-3200 range in any gear. If I hover it there, the engine seems to lose power. Doesn't seem to be a transmission problem as it happens in any gear. Also, just before engine "coughs" I can hear a click from the engine. Not a rattle and not repetitive, just a click and then loss of power and then back up and loss of power. Until accelerator is released a little or increased a little.I was thinking maybe a fuel supply problem or throttle? Let me know your suggestions