[Gav]

I would change the plugs, as Bobby said, my engine misfired then died all together.
I can only assume that the plugs where old (40,000k's), had sat for ages and then was started and stopped and not really run for any lenght of time.
If you are ready to go through reg and are beggining to drive, you are mad to not change them and rid yourself of a potential problem.

Gav