Running Rough at high RPM??

I just purchased a 2001 XR650R that has very very low miles on it for $3000. It still had the original tires on it when I got it. It had been sitting for awhile, and when I got it the float kept sticking open and the carb would dump gas when I stopped. The bike is completely stock except for a Yoshimura Silencer(stock headers) and I need advise. The bike runs O.K. at low to mid RPM, but at high RPM it cuts out. I just cleaned the carb, and it was full of brown residue(varnish) and all the jets were plugged with goo. All is relatively clean now, replaced gas and I need some recommendations. Am I right in assuming that I need to rejet the main jet? What jet do I need? Also should I change the pilot and needle. I want the bike to run crisp, and I am not afraid to spend the money to make it happen. Is it worth it to swap the Yosh exhaust for a complete system, header and all? Also what air filter should I run? Any other mods I should do, I plan on racing this bike. Please help :banghead:

What jets are in there now, needle clip position etc. Has the bike been uncorked?

Carb is all stock. The main jet is a 160, and I forgot to check the pilot jet size, and the position of the clip on the needle. As for the uncorking, I honestly do not know what this consists of. I saw something posted on and I understood most of it except for the manifold replacement, where is this located, and if I have a Yosh silencer, do I need to do this?

Thanks in Advance.

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