Is there any power gain for an OS 120 Surpass III in using a pitts style muffler instead of the regular stock muffler or is it mearly an estethic reason for using them? What other advantages does a Bisson muffler have?

Different Mufflers have little effect on the output of a four stroke.

mearly an estethic reason

Ok, is there any weight difference btw the two?

There is no advantage to a pitts muffler other than your ego or what you think looks best of if you have another $75

I don't think Bisson makes a Pitts for the 120 Surpass?

Slimeline makes one for a 120 Surpass on it's side...

http://www2.towerhobbies.com/cgi-bin...?&I=LXFH01&P=7

Ok, thank you for the information.