250sx exhaust ?

[mikey's250sx]

are there any cores or plugs in the exhaust i can remove to gain a bit more power? i don't want to spend the $ on a new exhaust but a bit more power never hurts anything.
any other free performance mods to be had?
if i pull the airbox lid off do i need to mess with the jetting to compensate for the improved airflow?
thanks.

[4cylinders]

hey, pull the front pipe off the engine, and taper the weld in the end of it. always helped mine.