As far as boost spike is concerned, the following is based on my experience with my car. To be honest, this may be more for the lower end specs like my current setup than the higher ones!

With my car as it is, it means that I can run higher sustained boost, because the small spike does not exceed the capabilities of the car.

EG - Stage 2 Boost setup with Bayjhoo chip (pardon spelling) has a built in max boost of 28psi. Lets say you were trying to run 25psi sustained (probably too much to be honest). What would happen is that with the old setup, to get anywhere near 25psi, the spike was going over the 28psi, causing the chip to override, and cut fuelling - result not good.

So in a nutshell, the better the control of the boost spike, the more boost you can run as sustained!

This could be peculiar to my car, but since the boost controller was fitted, it holds boost way better all the way up the revs. Still a small spike, but less tailing boost at the other end!

Soo - less boost on the spike, more boost everywhere else!!!!

Hope this is not horribly misleading.

JJ