Trewer words were never spoken!!! I just had an exhaust valve rocker come loose, truth be known I think I forgot to tighten it after adjusting, my bad. It came all the way loose and allowed the push rod to work it's way under the lifter keeping the valve opened. No compression no run! First time I have ever done that but things do happen.
I never shoot for any special RPM, I use the tach to make sure I don't over rev the engine when I'm looking for the prop that will fly the plane the way I like it to fly but stay within the working RPM of the engine.
For tuning the engine I like the tach so I know when I hit the high RPM dead on then I can see when I get it backed off 3 to 500 RPM, most the time I can do it by ear but not always. My 100s aren't touchy at all and can run well even when they are too fat but don't run well when lean at all.