Re: No need for speed
Even though the kits are 'identical' they still vary considerably. Manufacturing Quality (Read: consistency) programs in china basically don't exist, So what happens is that you get motors with sloppy tolerances. Sometimes you get a good one, Sometimes you get a seriously sloppy casting, over/undersize parts, and bad bearings.
What I would do in your situation is Research the crap out of 2 stroke tuning. MacDizzy is a good place to start. Beyond that, All I really did was teardown the motor, look for anything rough, slagged up, or misaligned. Dremel everything to match: Transfers, transfer windows, exhaust port, intake manifold... I mean, just check your intake port at Top dead center. You'll see what I mean, as the piston skirt is probably blocking some of the port. Scribe a line on the piston, teardown the motor, and cut away the area on the skirt that was blocking the intake port. Make sure your piston comes down to the exhaust port's floor at Bottom dead center.
Things like this will improve performance and give you a smoother running motor than any aftermarket performance part. And it'll make the gains from all those shiny parts bigger.
I should organize a sticky or something for a quick guide to hand tuning these beasts