If an engine taps under load when moving, shouldn't the same sound be heard with it sitting still, but high rpms?? Need to know soon! I have some tough choices to make.

Sometimes, but not necessarily.

 

Some noises have a specific RPM range that they'll occur at, other noises have a specific load condition that they'll occur at.

 

e.g. Main bearings will tend to make noise at low RPM under load, whereas rod bearings will tend to make noise at elevated RPM with no load.

 

Then sometimes temperature is a factor.

 

Most folks would tend to attribute a tapping noise to something in the valvetrain, like a stuck lifter.

Well this noise is heard under higher rpm and under load, when accelerating. I am pretty sure it is in the exhaust resonater (aka mini muffler) area or converter rather than the engine itself. But the sound is similar enough to a upper end engine noise that I was concerned. I cannot hear it standing still at high rpm.