Zilla is on point with most of his post. Albeit, I did see some HP gain on my big bore stock cyl 4mm motor. Only a couple ponies though. It isnot about making horse power, it is about creating reliability
That dude Joe Molinari keeps barking off that it will double the life of this or that, but that is nonsense. I have seen great results though and have been Cryo treating parts for about 6 years now and I will continue to do so. As I am also a proponent of engine coatings, I would suggest doing your Cryo treatment through Mach Modified. They can Micro Polish, Cryo Treat, and also do a slick coating on parts that benefit from it. (ISO blue, Slick Blue, Turbo Blue, etc.) http://www.machmodified.com/micro-polishing/
Look at 300below.com for some cool stuff that it can benefit. But do not go through them. Yes they were one of the original companies offering the process, but they have qouted me twice and fucked with the price both times and it was a shit show.