I have his basic +4 right now. It's about 1 gallon and gets better every time I run it. I'm really liking the fact that it is both smooth and has gobs of power everywhere. There is no part of the powerband that comes on too hard but it does not lack anywhere and will allow your buggy to do whatever your throttle finger dictates. No wheel spin but definately enough snap to clear anything with the right clutch set-up and tire choice. I'm running mine with the 2090 pipe and just now starting to get the really good runtimes. We have a big race coming on 11/4-11/5 and I'll be running my clocked B5 and my clocked +4 in possibly 4 classes.