I have $600 bucks now to put into the engine of my YFZ, what should I do to get the most power for racing up bowls in the dunes because thats pretty much much the only place I ride. any input would help, lat

 

Get a pro-flow K&N airfilter and an aftermarket exhaust.
HMF and DR D make a great slip-on, and the power will be like night and day!![img]i/expressions/face-icon-small-happy.gif[/img]

Of course, you'll need to re-jet after this too.
If you need help in that category give me a shout. Looks like we ride in the same areas (Oregon dunes).

EDIT:
I just saw that you said putting money into the engine. If you already have an exhaust and intake, then you might want to look into an aftermarket piston and or cams.

 

High compression piston and race fuel.