Maybe, but why would a TC not slipping at high gear be a problem? It's not supposed to slip in high gears. It's when it's not slipping at low gears, that it would be a problem. You really need that manual gear box don't you?! The only converter I'd be worried about in this case would be your catalytic... but you said you've got a fairly new exhaust.
(PS, you might have more luck getting your answers in the E36 part of the forum) Not that it's a big deal, of course.