Echo CS-550P saw was having issues. The owner said running but not well, 145psi they said, needs a carb clean..... Not the issue, this saw was run very hard with little to no regular maintenance. Appeared to be cutting balsam or pine of some sort. A full inspection revealed 3 out of 4 head bolts backed rite out, may have had compression but no seal for vacuum. Made it seem that the saw was having a carb issue. Re torqued and then figured out what the carb is set at with out the limiter caps.