Thanks for the replys.
I don't think timing belt is responsible as it was only changed a few thousand miles ago and made no difference. Not sure about engine mounts but they seem in good condition. Something to think about though.
Tappets were adjusted less than 2000 miles ago, but didn't have any effect. Air filter was also changed recently. I'll have a look at intercooler.
Just found a couple of other things, after cleaning the pushrods yesterday, one of them seems to have been subject to a lot of heat (the one with the damaged tappet slide.
The air filter has a rubber thingy on it (drain) which appears to be open all the time.