I've done business with Z1 for over 7 years and never had the first issue. With a Z1 built and tuned engine making over 700rwhp with Z1GT675RS turbos, and STOCK piping, my car is a perfect example of their capabilities. Unlike most members on this forum who only run race gas long enough to tune and make big numbers on the dyno, I regularly drive my car on the street with the 700 hp tune not to mention multiple HPDE in the middle of summer. With over 15K miles on the built engine over the past 3 years I don't think there's any questions that this shop knows what they are doing.