yea... i think that in all reality, twin turbos on most applications end up being counterproductive.

the only exception to that is on V-style motors, W-style motors, or anything where the physical placement of a single turbo could be less efficient that two smaller turbos (like plumbing a single turbo on a V6 or V8; too much charged volume, makes more sense for two smaller turbos right on the exhaust manifolds on each bank)

on any other setup, (i.e. inline 4s and 6s), the friction and energy loss of driving two turbos almost always negates the quicker spool. and the other thing is, the applications where you would want a quicker spool to make the car faster (like stock supras were) can be surpassed by getting more power out of a bigger single. so it wont spool as fast, but you end up getting better power characteristics from the single anyway, so even the slightly longer spool is negated.

...as far as i understand...