I sort of subscribe to this lovely aussie magazine, Performance Imports and on one issue last year they did a feature on this 700hp s15 by Scorch that has a VE headjob. 700hp is a bit overkill for daily use but in that one, he made do with a HKS FCON V-Pro.
No cutting of the firewall is required, but you have to relocate the CAS and a whole host of other head ancillaries. Currently MAZWORKS USA has a complete kit but its too expensive. A look at the pics on their website suggests that custom billet relocating plates is all thats needed. I'm now in the process of finding a good neo VVL engine that i wanna tear apart and do a detailed comparison study. Other than that, browse thru the wheelsjamaica forum or trinituner forums. They are good at this conversion and have some good discussion threads to learn from.
Cheers