i removed the box lid on my 300ex, i plan to jet it, i bored it 20 over, i have stock exhaust, do i need to put an exhaust on it?

 

You don't need to, If you got an aftermarket exhaust you would gain a bit more power. The 3 best budget upgrades are exhaust, intake, and correct jetting. By removing your lid that is step one. Try to get a good foam filter, Uni makes some good stuff that is better than stock.

 

Get a full exhaust system! That stock header is pathetic!!!

If you get an FMF PowerCore 4 or Q, it comes with a header.

 

the stock pipe is puny and a joke. go for a header pipe and full exhaust with white brothers or something,theres are really good for the 300. i also have a k&n for air filter and one size up on jets but i run with the air box lid on.and if you bored it you definitely have to jet it. and the powercore is good just as recon suggested.