What ever you decide, get it dyno tuned.
Not sure where you are, but a reputable shop should be able to dyno tune your MAF. That way you can dial in the specific profile you want (low end torque, high end power, fuel consumption...). If you are on the east coast I highly recommend Mario at Vintage Sports Racing. He's done this many, many times with all the classics (e28/e34 M5's, E30 M3's, M6's...).
Gettin' cold in NH,
Bob K88 ///M5 2875369, RIP