In-line filters are a must with these things, the tanks are not lined, tend to be a touch rusty and mine is still spitting little bits of paint into my filter even after 700 miles lol
I shoulda lined it
It defo sounds like you got an air leak somewhere, tho I'd suggest sticking a lil o-ring in the carb where the manifold seats and checking/replacing the intake gasket with a real one (the stock ones are almost useless in most cases) - with two strokes you could be suckin' in air from almost anywhere.
Check all around both the upper and lower gaskets on the cylinder - lookin for "soot" or greasy nastiness near the head and base gaskets, often the headbolts weren't torqued properly at the factory and/or sometimes the milling process leaves a bit to be desired. Check the gasket seam where the two halves of the crankcase join and take a look at the base of the clutch's cable guide (nearest the clutch arm), this cable guide wasn't tightened enough on mine and was leaking a bit.
Lastly - there's the couple of bearing seals, look for excessive oil in your clutch housing and magneto, fortunately it's unlikely it's those with a newer motor.
Odds are it IS simply the intake manifold - specifically where the carb mounts. It's not a bad idea to keep an eye on the other stuff though
Just as I suspected, it's gonna be stubborn.
