aye all the extra piping is a PITA to do twin turbos... TT's are better used on motors without the clearance to provide for 1 well placed large turbo.. aka the Z32.. Personally I think that the only reason toyota went with twin turbos for their supra was because they have alot of those CT's lying around and nothing better to do than make the car "SOUND" cool (OK so 2 CT's are cheaper than a T4 or something lol, i dunno)

TT's are a waste inless you absolutely have an engine configuration to make a single turbo's piping a nightmare (read large V6 or V8 in an engine bay, dont want pipes taking up all the spaced needed for accessories...)