My beloved 2wd saff has developed a knock/rattle.

The noise is apparent on idle and on over-run but goes when on throttle.

I have replaced the tappets hoping this may cure it but it did'nt.

Also the noise comes and goes so one minute the engine sounds sweet and then one minute its shite. (i've noticed it gets bad after a good thrash!)

Any ideas on what it could be?