Turbo losing power on full throttle

How Do all,

Anyone got any ideas why my Octavia vRS's turbo is losing power at about 3500-4000rpm, on full throttle....? It just loses all boost and has nothing left - If I back off the throttle slightly, then it'll keep revving up, but nowhere near as quickly as it used to. It makes a squealing noise at the same time it peaks and just sits there gaining nothing with my foot flat on the floor. It's like having a 4000rpm rev limiter - I know what a diesel feels like now!! (Only kidding don't be too offended!)

As it is throttle / load related, i hoped it might be something simple like a pressure hose off, but haven't looked yet - any thoughts...?

Cheers.

Steve