yea, 99-01 RS's are SOHC, the 98's however were DOHC. do a search, youll fina a lot of stuff. the most reputable tuner for the RS is probly cobbtuning though..... www.cobbtuning.com
, but theyre specialty is N/A. i believe the ludespeed is the most often bought tubo kit out there presently, but there are several others.
couple other links you might want to check out, for some real basic parts....