they get to 60 in just over 4 seconds as they are
will only be used in anger on the autobhan or santa podYou could gain extra points on your license, 12, and you could lose pounds walking...
I assume the turbo is non-factory fit.
If it is, I would echo S-A-M U-N-I-T and caution against wringing any more power out of it if you're lucky, the diff or gearbox might kark it, if you're really unlucky, you could snap a con-rod.
Ive got to ask what does a bi turbo do average mpg?
I think that 14 mpg would be nearer the mark at the best amd 9-10 around townBit better than a challenger shuttle, but not much.
Cruising is probably 20 mpg or better (and might be surprisingly good as the engine is dawdling).
Driven as fast as it will go, I suppose mid single figures.
Really economy would be the last reason for having one, especially if you want to increase the performance even more.