[esfkotaro]

As I recall reading (I may be mistaken), Leno's car ran, but only just barely. It was entirely unreliable and not really drivable, mostly due to the lack of proper ECM tuning. I believe it DID produce the 425 on a dyno, but I'm not entirely certain there either.

As explained before, the difference between a single turbo and twins is more in the reduction of lag. By using 2 smaller, easier to spool turbos instead of one larger turbo, you can achieve the same level of boost faster. The benefit of a single over a twin setup is primarily price, but also in simplicity. More parts = more problems.