My mates just limped his Cossy home after his turbo is randomly cutting out.

It try's to boost then just cut's off boost as if it's over boosting and won't go over 4000rpm.

Then the next moment it's fine for a short while. It has started smoking a little more than normal.

I thought if a turbo went it would pretty much just go bang and that would be it?

I:E it would work or not...

Any ideas anyone?