Thanks for the response Dave.
If the throttle is held when the vibration occurs,the vibes stay,back off and it goes.
Will be swapping shafts this afternoon from donor vehicle.
Reason for trying tandem pump was that a friend and ex Audi mechanic thought it could be injector misfire due to lack of fuel pressure.
Also forgot to say that I took the car to the main dealers to upgrade ECU software,their w/shop manager said fuel pressure should be checked next.
It was easier to try another pump from donor car which was a known quantity.
Software upgrade made no difference.
Let you know what happens with the shafts, cheers,D.