Lazy Pilot,
Yep, the TT 42 is real light. The engine and mousse can combo should weigh no more than about 12 ounces. I'm not sure what the 42 and stock muffler weighs, but I've seen several cases where you'll save a little weight with a mousse can setup over the stock muffler. The mousse can itself will run 1 to 1.5 ounces, depending on what type of can. The header should be 1 ounce. I'd say the stock muffler weighs around 3 ounces or so. The nice thing is getting a performance boost without adding weight. The Ultrathrust muffler will definitely add performance, but those things are pretty heavy. They are built like a tank, they will probably last forever. I don't know anything about the black Mac's mufflers. They look nice.