I also reccomend the Tower muffler. It is cheap and easy way to get a few hundred RPM. The GP42 is no power house but it should do the trick for the Superstar 40. ANother thing to consider is looking around for a cheap TT Pro 46. I have a few of them I have gotten used for $40 or less. They pop up quite a bit at swap meets and on eBay. I lurk on alot of boards as well looking for classifieds.