I wouldn't touch anything this guy does with a ten foot pole.
I actually went to visit him at road atlanta when he was getting going and evidently he left Germany with quite a mess behind him.
Also, you have to be careful regarding what it is you get from them. You may very well get a certain amount of horsepower but whether he is changing everything that is necessary for longevity is another matter so do not assume anything that because you are getting horsepower it is useable for your driving style or that you are getting top quality parts either.
In short there are other tuners out there and I have dealt with a number of them. I have had good experiences with RS tuning, Techart and Gemballa. The experiences that I have had dealt with fairly extensive mods such as engine replacements, suspension upgrades and we had the parts sent and spent the time doing them.
I would be happy to refer you to someone that did a great job for me. If you want to check out the types of stuff that we did for ourselves you can look (enter into your address bar)
http://www.zoomzoomvroom.comHope this gives you a few ideas.