Steve Bliss sawed open a Mexican ABA head to see what the ports look like. He posted the results on this thread on old Hardcore VW (the real forum has moved to VWSport).

As you can see, the short side radius of both intake and exhaust really leaves a lot to be desired. The roof of the exhaust port has a really nasty venturi at the guide boss. Get a German head.

A 2.0 l 16v (9A) dissection done by OttawaG60 on Vortex. Here is the original thread.