en me baladant sur le forum mgt je suis tombé la dessus :
Powerstrokes - Early this past season (2005) I (Chevy-SS) was racing at a track with a tough whoops section. My MGT was very touchy in the whoops with the stock shocks. The suspension could not react quick enough. The next week, I put on the new Powerstrokes and I could take the whoops at full speed. It was a real noticeable difference. Initially, I used the stock setup, which was the red/yellow springs and the 30w oil. This was very soft, but man, it really just soaked up the rough stuff like I was floating on air. A softer suspension is a little harder to drive, but I kept it like that for a couple of weeks. I eventually had to stiffen it up a bit as there was a little too much bottoming out. Now I use gray on the primary spring (small one) and yellow for the secondary (big one). I run 40w in the coilovers and 50w in the bypass shocks. So I would recommend the gray/yellow, with 40/50 oils. I mount the shocks in the outer holes on lower arms and set suspension at "bones level". That should be a good starting point.
j'ai grosso modo compris l'essentiel mais je ne sais pas a quoi corresponde les indice d'huile en indice que je connais moi, c'est a dire 500 600 etc la c'est du 40w 50w
et bon faut que je revois le système 
)
