Lost Power? But idles and runs smoothly?

Fuel pump ''could'' be leaking into the engine causing the oil level rise. Check by removing oil cap and smell.OR pull the dipstick(away from the car) and put a match to it. Common problem. I also had a coil that was going bad and the car would idle fine but had no power.Just a few thoughts.
Valve lash''could" tighted from valves receeding into the head because of non hardened valve seats but may take many miles for this to happen between valve adjustments.

DEEP CREEK, Fun place rented a cabin there a few years ago.