If the car is stationary and I rev the engine I don't get any visible smoke.

During the day I know it's there but its light in colour so can't really see it.

But now it's dark early, I can constantly see it in the headlights of drivers behind me and there's a lot!!

It's only under heavy load/acceleration. I'f I just pootle off from a set of lights then I see very little/none.

Any ideas?

I've quickly checked my IC hoses and I can't see any cracks in the common places.