Cleaned boost solenoid at the weekend. It was o.k.at first but now its over boosting.Have i knackerd it?.

 

I had the same problem. It may be you have dislodged a piece of dirt that has got stuck in the restrictor on you first clean.
Or a pipe has got a split in it while you have been taking them off and on.
Give it several cleans and double check all the pipework as I managed to split one of my pipes when I was putting it all back together.

Stuart