Was at Auto salon Singen today and saw a lowered TT, which looked awesome, how can I lower my car 15-20 mm without altering the ride ??

 

Get the JIC coilovers. Your ride will be lower & more complient. (Unless you drive over a large bump)

 

looks like Eibach springs might work too ?

 

I was in your same situation 6 months ago, considering all the options. ROW is the most reasonable but not adjustable. If you are going to spend the labor in installing it, you should consider PSS9. I purchased mine from AWE tuning and the ride is softer on straights and handles much better than US spec factor suspension. Setting below 4 is softer than factor and setting 1,2, &3 is stiffer. The nice thing about PSS9 is that if you don't like the height, you can adjust it any way you want and realign the car. I don't think the ROW is low enough to be worth while, just my taste

 

He's already got ROW since he's in Europe.
Richard, a friend of mine tried techArt springs and says that the ride is not that much changed over stock. I guess you're in Switzerland, so you could try Sportec. A full coil-over is much better though and the labor for the instal is the same, so think about that.