I think you'll be much happier if you get a jet kit. My 96 GSX-R 750 was totally strangled by the factory carbeuration and pipe. A slip-on and jet kit made it into a totally different bike, honestly! It was much more responsive after the upgrades. An engine jetted lean will only get leaner with a free(er) flowing exhaust. Put a jet kit in and be done with it, you'll be glad you did! Just my .02 by the way.
P.J.