After reading all of the good things you folks have to say about muffler modifications, I just ordered a modified muffler from Walkerssawshop.com in Canada for my MS 290. I didn't want to chance it and ruin my stock muffler b/c I'm clueless to this muffler mod stuff. It was $48.00 total (shipping included). I guess it's not 100% necessary, but it'll be cool! ! !