@echo I would worry too much about the altitude thing. I realise this can have a small effect over a large altitude change. I live at over 1000ft and tune my saws at home and regularly work by the coast with no noticeable difference in performance. Your little echo may behave differently on cold days etc but if it starts idles and revs up ok and spark colour is good I expect you may be overly concerning yourself. Regarding a new AT saw, both 550 and 261 have had issues, these seem to ironed out now and there is a new mark (barry) 2 550 out now, which should be out now. Quite a few folk I know have issues with both the husky and stihl saws you mention, but alot of people love them and have had no problems.....so who knows? Are you set on buying new? If I lost all my saws and had to start again, I'd be looking very seriously at the echo/dolmar/makita offerings. Whilst decatting the dolmar/makitas/echos seems like a sensible idea, I haven't heard of alot of big issues with them when left in. Possibly you might have to clean it after a few years work. However less people run these saws so you may not hear of the issues as often. I have decatted all of the echoes, makita and dolmar saws I have. Partially because I cant help myself from fiddling with them, not because i thought they were being restricted by them. If you want to buy a new AT saw, I would go with whichever dealer seems the best service rather than which brand, as quite possibly you will have some issues. Even if this means having to spend a 10er to post it back to them in the event of a claim. I have never heard of a warranty claim being refused from not having receipts of regular dealer servicing, however perhaps a dealer on here an shed some light onto this.