au miss fires at idle and low rpm of 1000 or under.
leads have been replaced.
coil packs are fine.
spark plugs have been replaced.
no major engine noise.
does this on both gas and petrol.
does this when motor is both hot and cold.
diagnostic check revealed nothing.

any ideas please?

Does it break down badly, or does it sound like it's running on 7?
If it's doing it on both fuels then it's obviously electrical or mechanical.
Have you given it a compression test?
Have you actually tried coil packs on it?

vaccum leak?