Alot has to do with driving, tires, road conditions, and etc.
I've beaten GS-Rs on the street AND track with my GS(ls) because I know how to drive.8urcivic can vouch about a supercharged GS-R(JRSC,LSD trans,short shifter,i/h/e/,lightweight unorthadox pulleys,...etc..etc)in our area running no better than 16s(cant remeber exact times) b/c driver couldn't handle the car worth a shit..... I'm not trying to 'ebrag' or whatever , but its true. I had a video of me running those times in my GS, but my house flooded and ALOT got damaged. (a year later and I'm still rebuilding...) Just because you "smoke" ls's doesn't mean that I can't run 15s...besides even -if- I was bullshitting, its not like 15 is an AMAZINGLY impressive time like ZoMg y0...I get SO tired of people telling me their car is faster than mine. I enjoy racing, but I damn sure don't have the car I do now for sheer speed...:roll:
EDIT
http://www.youtube.com/watch?v=Mnby1U8UmKI
According to that link , ITRs run 15.5s....with PROFESSIONAL DRIVERS