I had a Yank ST3500 and upgraded to the SS4000 and I absolutely love it. It drives almost exactly like the 3500 did in town, but is much more fun at WOT. And I do have 3.23's. It is plenty tight for me, and low rolls are a thing of beauty. It has a 2.6 STR which makes it nice and tight for daily driving. The only downfall to the STR is how hard it hits. Traction is hard to come by with Nittos. I've cut a best 60' of 1.72, and that was rolling into the throttle. With some better tires, it'll cut some hellacious short times. I would go with Yank's recommendations though....they won't steer you wrong. And I would definitely go with Yank coverters. They are the best in the business for a reason.

They are extremely efficient, and they are rated right on the money. Vigs are the ones underrated, but they have a damn good converter also.