Bob I have a 3W 50 with supersonic muffler, I could not get to the neddles on this either. A poor design maybe. I took the muffler off and put a dent in it with a 1.5 inch pipe about a 1/2 inch deep, this gave me plenty of clearance. I also have a 3W 150 that the neddles were hard to get to , I sent the standard mufflers back and used a tuned pipe, cannister set to solve this problem.

Kent