There are two paths for the wind to whistle through on a 123 door. The window seal and the door seal. Both can be replaced. The door seals are between $60-85 per door last I looked and the window seals should be less than that. My 123 isn't worth restoring and the heater makes up for the losses in the winter so I haven't bothered with it. If my 124 started to do it, I'd probably fix it. I silicon all of the seals every year with spray silicon on a q-tip and the seals all look brand new. The car is a 1989 with 205 k miles on the clock. If anybody replies with the "don't EVER use silicon on rubber" line, please tell me what they think you should use.