Performance exhaust on stock gy6??

[tdawg92]

Hello everyone, I've been reading in the shadows for a while now and finally made an account.

So, I bought a 2010 roketa 50cc scoot a week ago bc my 2t adly noble 50cc broke down. So I needed new scoot to get to work until I fixed adly ( already fixed). So I bought the 4t with 1300 miles on it, came with Lo pro tires on 12" rims not 10" and a performance exhaust called "OUTS performance muffler" and says "DON'T TOUCH" under brand name. My question is, do 4th scoots come with these stock or did previous owner install it? I ask this bc my last 50cc gy6 I had was a lot faster(40-45mph no prob.) then this new one I have. I checked for restrictors..couldn't find any( didn't check cvt yet for one tho).. It will get to 20 mph no prob. But takes for ever to reach 35 and even longer to hit 40 mph and sometimes won't even reach 40.
I should also note it's has no balls what's so ever, when I'm at a stop at red light and it turns green, when I give it gas it Boggs and wants to die, If I give it more throttle it will catch its self and start accelerating, if I let off throttle when it does this it dies on mr in traffic.

So far all I have done to it:
Changes motor and gear oil with amsoil 10w-40 and amsoil 75-90
Changed plug with iridium one
Cleaned carb & air filter
Checked tire pressure

Still need to do:
Check compression
Adjust valves
Check how good spark is

So if my hypothesis is correct and the exhaust is not stock should I buy stock one from scrappy? Or would it b better to buy uni air filter and rejett the carb?? Also sometimes when I let off throttle it will let out a little " puh" backfire nothin to major tho.

Thank you everyone, all opinions count!
-Teryn