FYI, euro catless muffler installed. Ran much cooler! Beat the snot out of it, mostly with a "18" inch GB Arbor tech and 91VXL chain. FYI for those interested, on my bathroom scale - PS-421, catless muffler, full gas, full bar oil, "16" Oregon Pro 91 bar and chain (As Saw Troll pointed out, really about 15") = 13.2 lbs. For comparison - Stihl MS-261, stock 16" bar and chain (really 16"!), full gas, full bar oil = 15 lb.
Very happy with the 421 so far, though surely not fully broken in yet.