As coincidence will have it, I just returned from Angola yesterday
evening.

You are not allowed to remove ANY Angolan currency at all, and the
last check they do at the airport before you leave is to ask you what
money your are carrying. If they suspect that you are carrying Kwanza
or large amounts of USD, they will search you. It's never happened to
me, and I've been into Luanda many, many times.

I smuggled a few notes out of the country for my collection once. If
you get caught out at the airport, they will confiscate the money and
you won't get a receipt (ie: they keep it for themselves).

When I go into the little office at the airport, I always tell the
policeman in my poor Portuguese "Eu nao tem dineiro nacional, so
dollares Americano." He asks how many US dollars I have, and I just
show him my wallet with a few hundred Dollars and he waves for me to
leave the office. Never offer a bribe or be intimidated by the guy. As
I say, I've never had any hassles.

Cheers,
Marc