[wilkin250r]

I can't fix your problem, but I may be able to help identify it. Let's look at this logically.

I don't have a hydroboost, but from what I understand, they're powered by pressure from the power steering pump rather than engine vacuum. When you're brakes are applied, your engine almost dies.

Also, the engine starts to die when you turn the wheel standing still.

BOTH of those issues involve the power steering pump, yes?

It's starting to sound like you either have a general engine problem (vacuum leak, carb settings, ect ect) OR your problem is somehow centered around the power steering pump.