The copper spray works great with the viton coating on your mls headgasket. It helps seal to the head and block if theirs any imperfections. Expecially cause you need almost a mirror-like image on the head and block. Doesnt have to be the prettiest thing, just flat and clean. The copper spray definetly DOES make a difference. It also helps stop the mls hg from leaking oil if you use really thin oil/synthetic. ALWAYS hone out a cylinder if you're installing new rings. They will never fully seat if you don't. NPR ( Nippon Racing ) is one of the best oem style parts out there and work great for most. Make sure you use the arp lube on the studs where the nuts go, and a calibrated torque wrench.