Mine done 30,000 miles.

 

mine were out on 9k miles.

 

Could someone please explain how much of the system actually gets pressurised when doing a boost leak test i.e do the cylinders get pressuried up?

 

thats what a compression test is for

 

So where does the air your pumping into the turbo actually stop at then i assume it fills the inlet manifold which in turn would then go into the head and past any inlet valves that are open. I could be well off here but does it not reach the pistons in the end?

 

You got it right. Wheather the valves are open or closed will determine if the air gets to the cylinders. If open then air will reach and if closed it wont. For a compression test though you should be in the 160ish psi region on a cold engine. My TSi was 165psi on a cold engine across the board. So a boost leak test wont generate anywhere near enough pressure for a compression test.

 

my seals just failed me at 16K. they must be completely gone because im only holding 22psi for about 2 seconds maybe then it just falls fast. i start loosing boost at 4500rpm. no good