best mod under 20 bucks is there one?

[400exdirt]

Just wondering, my buddy is telling me about a mod under 20 bucks thats going to kick my butt, we already did the pipe, filter, sprocket, what else could be left that you could do under 20 bucks thats not obvious
please help

[bama400ex]

if you dont ride in water and mud remove the airbox lid and rejet it.

[Holty]

yep.....remove the airbox lid.....best mod period.

[VegasEx'r]

I have to make a couple of assumptions here (& yes I know what happens when you do that, but bear with me). Assumption #1: Your buddy has a 400ex. Assupmtion #2: He is going to actually spend money on this mod (not a "free" mod, like removing the airbox lid or choke,which BTW are both good mods). The only thing I could think of for under $20 would be a Sparks advance key for $15. I think that if the quads & rider ability are the same, and he has an advance key and you don't, he might beat you (in a straight line drag) by 1, maybe 1 1/2 bike lengths.