hectori,

how much air is there in the intake system (that means between the compressor and the closed throttle plate), on for example a t3 equipped cossie with 4x4 intercooler running at 15 psi and then closing the throttle?

how much more air is there with the same car but at 30 psi?

how much air is the engine consuming past the 'closed' throttle plate when changing gear and the revs are dropping from 6000 rpm?

how much air does that leave to 'rush' back out of the inlet past the compressor and do all of this damage?

how easy is it for the air to escape out past the compressor? it's not like a positive displacement compressor, it's just a fan.

have you ever blown across the top of a bottle? you get a noise, right? but is any damage being done to the bottle?

i am not saying that you're wrong, but consider some points.

incidentally, i run a t3 at 22 psi without d/v. i was watching a tv programme last night called 'greatest rally cars' showing the 3 door cossie when first rallying. these were also running 22 psi without d/v as you coud hear. i know that they do not have the same concers regarding longevity as a road car, but if there was any chance that the turbo would be broken on a rally, i believe that they would not do it.