All,
After leaving the engien for a couple of days idle, I always find a tiny smear of fuel on the block (very small). When I wipe the fuel bowl covers with a kitchen wipe you could see the wipe getting soaked (not extremely) with fuel. What could be the cuase?

The carbs came from Andy of AB Performance, stripped, cleaned and re-jetted and they work absolutely perfect.

I have tightened the float bowl screws, but is there any specific torque settings?
Are there any other areas that I have to look into?

Could be a float valve sticking?

Try checking the drain screws on the bottom of the carbs to make sure they're all done up properly.

When I first fitted mine they were leaking from the rubber seals on each of the carbs where the fuel supply T pieces go in to the carbs. To replace them you need to remove and seperate all 4 carbs. Whilst it's appart you may aswell do the breather seals too.