Fuelman has hit the nail right on the head!

Slobbery rich breakin won't usually make an ABC engine unusable, but, if everything is equal between engines, the one run slobbery rich will NEVER perform up to its pre-breakin potential.

If that performance degradation doesn't bother you, then by all means make'em slobbery rich for breakin.

I thought I knew quite a lot about 2-stroke engines but I wasn't having much luck with engine performance which was a bad thing when you are primarily flying pylon races. I started to observe what the guys who were always winning were doing with their engines. One of the pilots who had set a Q500 speed record at the AMA Nats took me under his wing. Well, I quickly realized I really didn't know squat about ABC and AAC engines!

To make a long story short, break in your ABC or AAC engines the way Fuelman broke in the number 2 engine in his post if you would like it to perform to its full potential.