I have to second the idea on the Tower .46 muffler. I found out about the performance improvement by accident....I lost the back half of the OS muffler in flight. OS won't sell just the back half and they want 24.95 for a new muffler.

Tower sells the Tower .46 muffler for a lot less and it qualifies for their special 3 day shipping.

I was the most surprise person when after installing the Tower muffler my Tach showed almost 500 more RPMS with the same fuel and prop.

It is a bit louder ......but it sure pulls noticably harder. I'm not running any leaner still have visable smoke showing.

Try it you will like it.

P.S. I have 2 front halfs of the OS mufflers if someone needs them (cheap)