I have a 550xp that I got new last summer, and have put about a dozen tanks through it. It cold starts relatively well, and runs strong. But, it doesn't like to idle for very long, and it stalls a lot, right when I touch the throttle after idling. And it usually takes a 5-6 pulls to start after stalling. I've had other huskies have really rough break in periods, and turn out to be great saws. So, I'm trying to be patient, but I also don't want to be ignoring any problems. I did just notice what seems like an unusual amount of grime inside the air filter. Don't know if it's related, but I'm definitely throwing a new filter on it.