Fried XJ8 Engine

[Fly Fifer]

After frying my XJ8 3.2 engine, it was found I had warped the heads. Had these skimmed and its all back together now and runs lovely.

However, this is with the exception of at very low revs, eg tick over, when it vibrates so much you can feel your internal organs shaking. It's worse in drive, but still noticeable in neutral. Also seems worse when the engine is hot.

Any ideas would be really appreciated.