If I blip the engine from tickover just enough to get the turbo to spin it either (a) hold the higher revs for 5 secs or so then returns to tickover or ... (b) revs with a very loud knocking / tapping noise and tons of white smoke from the exhaust! Switching off the ignition does not stop it immediately only shoving it in gear and using the gearbox to stop it!
I have removed the air filter (was ok but with some oil contamination). It has the standard breather arrangement that goes in before the air filter. I have also disconnected the breather and there's not much top pressure.
Any help with this much appreciated.
Jon