[B]What should it get?[/B]
 

I want to buy a Haltech but I don't know what version is the best.
Does any 1 knows which one is the best for a 88 S4 Turbo II.

Well, the newest is the E6X, I believe. Basically a quirkier upgraded version of the very popular, but discontinued E6K.

Comes with better windows software. I certainly prefer it over the DOS, mainly because you can have multiple maps open at a time, and the correction maps have numbered, scaled increments. Also, you can cut and paste map sections. The gauge display panel in the software is nicer too.

The E11 is the more powerful and expensive Haltech. Resolution, among other things, is much greater. It's slight overkill for 2 rotor applications, IMHO. But, it does have a much more refined secondary staging method.