I really love the V4, have mapped quite a few and have currently got one on my turbo clio, its a really nice implementation of the megasquirt setup, its a professionally built unit and things like boost control are really sophisticated compared to litter like Omex 600 setup which is in a similar price bracket.

However like Jonboy says, I believe that Mtec are no longer selling them so its only an option if you find a 2nd hand one, and the trouble with that is what happens if you have problems with it down the line and cant buy a replacement?

Unlike Jonboy I like the version of firmware on it, its really stable IME.