it's an MTA-2 (MX3) Pocket bike, and that is a cag motor. performance pipes almost always require some work to fit, my ADA racing pipe on my blata was a nightmare, now I'm trying to fit a Jet Pro pipe in a Z-Star mini quad, anothe real headache....if you have a pic of your new pipe it would help, and show where it doesent fit..
There is alot you can learn in the air cooled section as far as tuning goes, and I suggest you take your carb apart and clean it... If you have a dremmel, there is alot you can do to get a smoother running engine such as porting the head/carb and polishing all the inner works.