sorry about the delay but here are the comparisions. all the saws are running 3/8x50x72 GB bars and new laser full chisel chains with 8 tooth rims. carbs set to husky recommendations. the wood is 8x8 tulip and each time is one cut. the cuts were all down. time in seconds.
372xp new out of the box; 2.94,2.77,2.58
372xp out of the box walkerized but stock muffler;1.93,1.77,1.86
372xp w/ appx 80 hrs with walkerized muffler;1.67,1.68,1.68
372xp out of the box walkerized with walkerized muffler;1.75,1.93,2.05
372xp w/appx 80 hrs;2.10,2.09,1.99