Stay away from zero gap rings for high performance applications, the C/A rings are the best of the bunch but still are more sensitive to detonation especially with nitrous or blower applications. I have used them before and they work fine but I like to gap my own rings and they makes it impossible to do. As a consequence the gap is larger than necessary (production tolerances) and they perform almost the same as regular rings on leak down.
Now if they could make a custom set for me according to my specs........
Outlawed tunes from outlawed pipes