So who sells the S300 or S400? I'm looking a twins also, since my wife got a new car, I can play a little more now. I was looking at the ht3b and the hybrid 40/35, along with keeping my tranny cooler. Is there more room using an S300 or S400?

 

The S4 is a little shorter.. and it rotates the other direction.. this allows you to tuck the inlet for the exhaust housing up closer to the block.. and let you have a staighter cool pipe from the outlet of the litte charger to the inlet of the big.. Makes for a little better looking setup..
Bryan

 

OK another dumb question, just to be sure, the S4 and S400, one in the same?? I like that idea of a counter rotating turbo, for the reasons you said.