Someone made this comment that I saw on another web site:
This may be a miles off topic, but the best solution to all these turbo problems with todays technology, seems to be to combine a turbo with a positive displacement supercharger, (with the compressors simply run in series). This has now been succesfully done on three mass produced production engines.
Nissan did it with the March, a small hatchback not sold outside Japan, it combined a Garret turbo with a roots blower.
Lancia did it with the Delta S4, again a KKK turbo with a roots blower, and two intercoolers.
VW are doing it right now with the Golf GTI hatchback just released in Europe this year.
I built an experimental system like this myself over fifteen years ago, the results were exceptionally good in all respects. The corporate bean counters are probably the only real obstacle to overcome, otherwise I am sure many more forced induction production engines would now be using this system.
It combines lag free low end torque, with high top end airflow. The advantages of being able to keep boost pressure just above exaust back pressure should not be overlooked. The torque curve can be made any shape you wish to make it, and it is relatively simple. Initial cost is the only real disadvantage.