Spent some time cleaning air filters on various machines this afternoon.
The Stihl blowers have a wire filter in the muffler that I used to have to clean almost fortnightly. These block with carbon and prevent the engine from revving, the best way to unblock them is to remove it from the muffler, scrape it against a wire brush and then refit.
Since using synthetic oil though, I haven't needed to clean them at all, and have been only had to inspect them on occasion.
This Stihl oil is pretty expensive for what it is, but the time saved by not having to unblock muffler screens makes it worth it. It also produces far less smoke than regular 2-stroke oil too.