The seller of the car had fitted a new fuel tank, fuel pump and all the fuel piping, before I bought it and it occurred to me that maybe the pump is too high a pressure.
Trying to second guess the thought process of a previous seller might lead you down the wrong path. The previous seller may have replaced the tank and pump to try and cure the poor running issue.
I'm not aware of the pumps having different fuel pressures. I have changed a number of fuel pumps on my aircooled and there has been no difference in specification.
If you're initial problems are caused by over-fuelling, altering the pump position will reduce the amount of fuel, but it won't alter the ratio which is why it's failing in a different manner now.
I am inclined to agree with Rusty about the float from what you've said. I've recently discovered 2 carbs that have had a float failure, I had stripped both of them several times and didn't discover the issue at the start:
http://club126uk.co.uk/forum/index.php?topic=11245.0I had poor running at mid -high revs.
excess fuel leaking onto the manifold, especially as soon as the engine was switched off
have you tried submerging the float in a closed jar of petrol? Pack something on top so it's entirely submerged and leave it over night.