The tensioner was well worn. I didn't realize how dramatic it was going to be until I compared it with a new one.
That tensioner was so shot that I decided to drop the oil pan and see if there were any plastic bits laying around, luckily there were none. Don't know where the pieces went since I only saw very, very tiny bits of pieces in my filter last oil change.
Before assembling the parts, I realized that the Iwis chain I got came with two E-clips instead of the older style fish clip. I've heard horror stories about the e-clips showing up in pans many miles down the road, so it looks like I'll be ordering the older style from Max BMW. Then it'll be time to get everything back together.