Rear lower body bits
 

On our '98ti at the rear most of the rockers just in front of the rear rear wells is whats left of a black plastic "water deflector??". Its not shown on Realoem but might come as a part of the item shown below. Right behind these is the only rust on the car and I bet its because these are mostly missing.

Any ideas and a part number??

#2 in "Rear floor parts" illustration on Realoem

Rear left side member 1 41118189975 $112.72
only in conjunction with stopper

Is this what you're looking for?

vehicle trim > insulation

Trim panel left 51718146205
Trim panel right 51718146206

On all 4 of my ti's these have been broken, probably from previous owners jumping up and down high kerbs. Even if they're still relatively intact they don't seem to stop wet mud collecting in a thick layer around brake pipes etc. I'm impressed you can see the rust under there & even more impressed that it's the only rust on the car!

Hey Ti Tinkerer, That's exactly what we're looking for!!! And yes its that clean.

The original owner never drove it in inclement weather and only took it to BMW for repair. It still has an OEM battery and spark plugs in it. My brother purchased it from him 2/2017 with 106k miles. ~5k per year. 123k on it now, all summer-time miles.

Normally we wouldn't care about something like that trim panel but the car is so 'unmolested' and clean that everything we do we try to make it perfect.

Thanks for the information.