Dude - I have an EVC4 (digital screen version) and it holds boost very very well. It also works with externally gated turbos as well as internally gated. And it works with single, twin, quad turbo, whatever.... Has a 2 stage function as well. I managed to install and tune it myself with no problems in 2 hours flat. And im not that knowledgeable with that kind of stuff, i just 'had a go'. Had my mechanic check my work and he was happy with it and mentioned he had put a few of them on GT-R's also. Im very happy with it. If you decide to get one, Im only too happy to help you set it up...
-rb25