mate i had a similar problem to you about a year ago.
the sound your hearing isnt anything, well since my car works fine and boost's hard. first symptoms were i was comming back from the GTR cruise and my car was spooling but it wasnt boosting. i thought it was the BOV leaking.... about a week later i was boosting it on the highway and "pop"my engine stops and i thought i was in a world of sh!t. took me 4 days to figure it out, and you can test this to if you want.
- my engine would start for 1 second and die.. with no funny sounds. -------- Rules out farked internals GOOD
- checked if any pistons were dropped, by removing spark plugs and feeling for pistons with screwdriver ----- u dont have to do this, this was an extra safety step.
- thought of the BOV's and checked them for any openings --- nope, all good.
- checked the turbo piping and its hoses....
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my intake hose on the intercooler had come off --- simple fix, bought a new clamp from repco and secured it tight.
the ticking sound stopped, so im assuming it was just the engines sound through the pipes.
i guess over time the pipes contract and expand everytime we boost and this time it just gave way. so check your lines and see how you go.
ps. when it stopped, the car wasnt boosting, it was pissing out smoke too... cant remember too well what colour it was, i think it might of been white.