Sounds like you are on the right track. Impulse hose, intake or crank seals are likely causes if it's an air leak. If it's a leak, it sounds like it will be severe enough it should be pretty easy to find. Compression is easy enough to check. If you don't have a gage, you can just pop the muffler off and look at the piston/cylinder wall to get an idea of the overall condition. If all looks good inside, it's time to start chasing after air leaks. If the piston/cyl is OK and there are no apparent leaks I also wouldn't completely rule out the carb. I assume you're versed in carb adjustments and have adjusted the low speed to no avail, so I'll skip all that. But I've worked on a lot of stuff, and every once in awhile I'll miss something in a carb and don't catch it until the 2nd look (OK, sometimes maybe more than 2). On you're oiler, I'm affraid I can't help. Haven't done much with those - never had one fail, so I haven't played with one.
BTW - Welcome to AS! Hang around here awhile and you'll find a lot of info, but you'll also probably find yourself with more saws! And don't pay attention to all the bad things that get said about 290/310's around here. They really are good saws.
Regards,
Shane.