Zo Greg D. Darryl ( SJ ) Spdracer Tim L. SilverTwin(OH) Greg ( Dallas ) Chuck S Steamy Kurt and the list goes on and on. I think it has to do with what Greg D said once. Flow pattern of 555's just works better for Z power curve. As we all can see, they can put out more power than any person will ever need for the streets. But there are those insane people looking for the Holy Grail