return to stock?

[woodchuck5515]

I have an 89 gs that The po put a vance and hines slip on. he also rejetted to god knows what. i am looking to get the the best possible mpg which means back to stock jets and maybe a 17 or 18t sprocket. my question is do i have to back to stock exhaust for stock jets and if so anyone know where to get one for cheap and for that matter the stock jets too.

[yamahonkawazuki]

complete exhaust, or the can? ( only)?

[woodchuck5515]

I think can only but honestly do not know how to tell the dif3