As if I have been is not possible... As if I had been his friend (some time in the past) is OK As if I were his friend (now, but I'm not) is the only alternative, I think, though it doesn't express the same thing.
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I think 'If I have ever been...' is a conditional, isn't it? That's what I was talking about, Pieanne
No, it's not...
"If I had enough money, I WOULD BUY a Porsche", that's a conditional.
M88, as if DOESN'T express a condition... IF does, but not "as if"; it's a comparison, but a fasle one