K14 efficiency/ boost pressure question

[simonh]

Can anyone tell me (or point me to another thread if it's been covered) at what boost pressure the standard K14 starts to just generate hot air and not improve performance?

I don't want to be running the turbo pointlessly hard but I'm pretty sure I can convince myself that the higher the boost pressure the faster the car feels. It's currently running about 24psi on the standard top mount, boost just controlled by fuelling. Can turn it up to run higher but don't want to needlessly destroy anything if there are no real gains.

Thanks.