It is a pretty tight fit to secure the plastic overcover on. I used the sandwich bag method to get the oiled foam saturated with filter oil as well and I used the Bel-Ray filter oil as well. If you do use it, wear latex gloves when handling the oiled filter as the Bel-Ray filter oil is nasty stuff to get off your hands and a tiny bit goes a long way. I never touched the carb settings as the saws run pretty rich from the factory and so far, so good.
Far as the muf goes, I removed the spot welded on secondary diffuser (which was a job because like I said, it was spot welded to the main diffuser baffle so I used a Dremel carefully on the spot welds until they let go and then I used some emery cloth to remove the remaining weld on the upper diffuser so it would mount flat on the muff. So far, so good and I also reinstalled the spark arrestor.
I run Red Armor 50-1 canned fuel and so far, no carbon buildup on the screen or in the exhaust port..
I probably will, at some point replace the 590 carb with a larger one but that is in the future. (I have it, as well as the 5 degree offset crank key and the ignition module but it runs fine as it is. and until the snow flies here, I really don't have the fiddle time.
So far it's been flawless with the Echo 20" greaseable roller nose bar and skip tooth Oregon chipper chain and it sure was a lot less expensive than a comparable Stihl.