Sounds like the bleed valve wasn't clamped in securely enough, and has blown off.

So........basically, your turbo will keep boosting and boosting and boosting until the weakest part of it lets go. Sounds like the bearings have shat it and the compressor and turbine has been fouling the casings.

My mates R5 GTT did this, he hadn't long had the car and it had a BRAND NEW (not recon) standard turbo from Renault, few thousand miles if that, pipe popped off the actuator and the shaft sheered clean in half

Bit of bad luck there but it could of been worse....?