Lot's of reply's in a short time. I've had the single and dual and currently have the dual. If you want the best and have the money, for day to day use I'd say the dual. The dual gives a bit more power under the curve while the single and dual are equal in peak power. For racing when your always at high rpm the single is KISS. (keep it simple stupid) I can make a case for either one. It's not an easy call until you know exactly how your going to use your car, what you want comes into play too. Look at your budget and make your choice. Both get the job done much better than the stock system.

Les