The engine that I had rebuilt by 22RE performance is a stage one. Nonwing I have not replaced my O2 sensor yet or the cat. So you passed with 20 mi on the new engine? I am thinking that the reason that my truck is not passing is probably one of these components. There are some hills that I have been taking the truck up, and I have been down shifting letting the engine wind down when I am approaching a stop sign. The engine makes good power, and is much more peppy than my original engine that had over 260K on it.

When a piston engine is rebuilt on a small aircraft like a Cessna 172, four cylinder horizontally apposed engine, the recommendations are not to vary rpm's much. They tell you not to do touch, and go landings. Where the power goes from low rpm's to max rpm's. They also tell you to keep the fuel air mixture rich, and stay at lower altitudes. For the first ten hours or so. Some of the recommendations parallel a vehicle engine break in, its interesting to hear all of the varying opinions for breaking in an engine.