My MS 290 didn't sound like it was running right. I removed the hood to see the air filter had 1/2" of dust on it. I thought about washing it, better read some tech about it first. Scrape across to remove build up, don't poke. Spray across filter with carb cleaner and air, not toward. Clean area with carb cleaner and air before removing filter.
I thought about changing the filter, not at $16. I went to ebay, 6 for $8. We have 2 MS 290's and a MS 310.