OK, driving along in my ERST as normal. Set off fromt he lights and jumped forwward, nearly stalling (my fault on the clutch). Then, it started to tap quiteloudly, like a split manifold.

Pulled over to check, manifold is fine, but a tap coming from what sounds like the lifter nearest the cam pully.

Turned it off, left it 10 mins, fired it up, sounded fine, if just a little tappy. However, underload, it was REALLY noisy, like I had done some proper damage. Really tappy tap tap kind of noise.

Been told it could be a collapsed lifter, but it's running fine, no missfiring or anything (well, not that I can tell). Then, just went to my birds, came back outside, went for a drive and it was completely silent, on and off boost, however, it has now started to come back again after 20mins of driving.

Please help-

 

The fact that it is changeable does sound like the tappet/s.
Maybe a good oil change and flush might cure it ?
tabetha