On both my bricks (1991 740 & 940SE Turbos) there is no airbox thermstat or the flap they control. I don't know if this is an option I don't have or if these were removed. The 740 is a daily driver, I have experienced no problems that I can tell from this stuff being missing. Any ideas?

Just for your info, i know that the GL non turbos had the thermo in them, though they are alittle hidden, my 86 it was pretty oveious where it was and on my 89 its hidden in and attchment portion of the air box.

On the 89, were you able to replace the thermo unit? If so, how did it come out?

It actually was pretty easy once i figured out how to get that attachment off the air box, youll first have to remove the entire air box and that attachment which wont come off without taking it out either way, once youve removed it from the car the attachement is held in by 2 inside clips, push the clips in and try to pull out, i gave up and just busted one of em in and pushed the other one as i was running out of time, once i pulled that piece off you can miss it it sits right in front of you and if you look at the other side youll see the little door in there too, i pulled the old one out, putting the new one in without breaking anything was the hardest part of it all, but after some thinking i just pushed like hell and was able to compress the springs ( youll understand when you see it ) and it slipped into place.

Turbos do not have this since the turbo itself increases the charge air temperature.

Thank you.