I have a 3400 Echo, on which I opened up the muffler, same as Brian did. It cut 10-15% faster, but was still a bit slower than an old stock Husky 335. Brian and a lot of guys like the Echo's, me, not so much. A good saw for sure for the price, tho. Just thought I'd throw in my feelings and cutting experiences, since they seem a bit different than brian's.
I'm a fan of the Husky 335, as most of it's old problems are solved. And if you have it modified for $120-250, it will cut much faster. Or just mod the muffler for plenty of guts. My Walkerized one is a great little machine..