If you look at where the outside air actually comes in from I believe improvements can be made. There are two little slots between the inner and outer fender, pulling hot (less dense)air off the road.

This will make the purists cringe! I cut a hole in the fender and used the little grille from a 245 wagon's right rear quarter panel to cover the hole. Actually looks factory. The grille deflects rain and snow and if you reverse it I guess it would have a ram effect?

I also blocked the flapper closed to prevent any hot underhood air from entering the intake. If it is just disconnected I believe you will still be pulling in hot underhood air.

I have the IPD 2 1/2" stainless exhaust and run 45 psi in the tires.

I carry about 80# of tools and spare parts (most trips run 1000-1500 mi.)and after these mods I started to see alot of 30+ mpg and one tank as high as 32.8 mpg. This is never below 65 mph.

It is an '87 745TI with M46 and cruise with almost 440,000 miles.