modded my Z, I researched, purchased the parts and had them installed by a Nissan mechanic in Annapolis, Maryland. I then drove down to Z1 to have additional parts installed and to have it tuned and dynoed. Zsh tuned my Z. Then I lost a piston. Hence my earlier posts about oil coming out of the blow off valves. I returned to Z1 for their Stage 1 engine rebuild and for some other cosmetic upgrades. Now she's 527.44 hp at the wheels and running strong. Any shop, person can make a mistake. No one is perfect. And if you want to stay safe, keep your Z stock. There are no warrantees or guarantees for aftermarket parts/upgrades.