>>is there a way to make the transmition shift later, like instead of 16mph maybe 22mph?<<
Two ways to alter shiftpoint, one is changing the clutch springs...complicated and based on principles most folks don't comprehend.....
The other is changing the sprockets, so that a different speed is achived at the same RPM - larger front or smaller rear sprocket would accomplish this at some cost to accelleration.
>>does it have a cylinder head gasket that i can remove to get more performance?<<
No, and milling down the cylinder head seal is a bad idea, because normal wear and vibration on it will eventually mill it down quite a bit unaided.
>>also can i make it faster staying stock?<<
Well, if you have a BiTurbo, you should upgrade the sprocket...you would get more performance at the top with less accelleration loss than you'd expect, the sprocket and BiTurbo combination seems to work unusually well for Tomos.
You won't get any more performance than that out of it in 'stock' form - however...upgrading to a larger carb would help, as would boring the original cylinder from 38mm to 38.5mm and getting the overbore piston and rings kit.
Hope alla that helps some,