I cannot speak for all their selectons. I have had a few sets of their CNC stuff and currently have one set on the dragster. I can tell you there Predator stuff is ok. My heads actually went to Slawko after coming from Indy with their CNC work. Tom did some massaging to them and they were certainly better, that with his valve job we picked up 20 average Hp. May not sound like a lot of this is a 1200HP deal. A second set were done right after mine were used for his new cnc program and that set is on a single 4 70GTX all steel all glass street strip car and runs 8's NA...