I’m working on rebuilding a MS 260 replaced seals, p&c and all the critical rubber. Intake and fuel line. Idles like garbage….it still acts like it’s getting an air leak somewhere I don’t understand it. Carb is the only thing I haven’t touched. I’ve got a pressure tester but haven’t tried that yet. Only thing I noticed when I tightened a couple of the head bolts they could have had a little dirt or grease in the threads on the saw, but I used new bolts. Used acetone and tried to get them as clean as possible. I’m kinda stumped because I don’t want to start tuning on something that I’m not 100% sure about. I’ve ran it a couple times and torqued the head bolts and they seem to stay consistent.