thompson1600
ArboristSite Guru
By adding the dual port muffler covers you should not be voiding the warranty. The dual port muffler covers are Stihl parts. Just remove 4 screws, take off the EPA cover and then put the new Stihl cover on, put in the 4 screws. If you do a muffler mod and cut into the muffler you would probably void the warranty. I'm not a dealer, but can't see that putting that Stihl dual port muffler cover on would void the warranty. The other thing is that the warranty is only 90 days on the 044, 046 and 066 which have the optional DP muffler cover.