header or no header?

[aldumoul]

stock 400ex. i dont plan on doing engine mods, im gonna buy a 450r eventually. but i want to get a pipe and jets for my 400ex because it needs to be opened up more, its not getting enough air, but is it worth buying a header and a slip on, instead of just buyin a slip on. especially since i am going to sell it this summer.:devil:

[underpowered]

in stock form, a slip on will be just fine, ecspecially if you are gonna sell it.

[aldumoul]

what slip on would you guys recommend? and what jets?

[TRX23rider]

i would reccomend the HMF slip-on it has great performance and it costs very little.