Its interesting that Tom did an E39 MAF conversion using Unichip.
Tom, must have cost you a fair bit, huh ?.
The gains he has, I am sure he is pleased with it. For the rest of us, this is a pretty serious undertaking, so think carefully before embarking on it.
Last year or year before, I corresponded with Tom about my home built 535 AFM conversion with Apexi SAFC2 piggyback. My aim was to get a bigger intake airflow in preparation for the Rotrex supercharger which I planned to install but changed my mind.
The mod itself is rather useful for me and I have enjoyed it since then. I have asked myself, why install the SC when I only need it for a few mins per trip. Using this Apexi, I can key in values and change air/fuel maps while I am driving or at the stop light. Works well. I even did track for a whole year on it. Never did miss a beat and has sometimes made me push a bit harder on the track!.
You know the feeling, after several hot laps and taking a rest, I used to tell my friend, after this run, I will go home or take it easy. Then my friend would say, "Whoa, so early, why don't you reprogram the Apexi to make it kick harder?". On a couple of occasions, it has made better laps times for me by changing to my known aggressive modes. Fuel consumption will suffer but what the heck, its on the track right ?. And i paid $150 for track fee right ? Might as well go for it. Good thing no incident with my car during the time. I am retired from track now. No fun in this car already, I am consistent within 0.2 sec per lap, so I achieved my objectives.
Been wanting to get an E30M3 but never could find one at the right price. Ended up buying a E34 Touring (stationwagon E34) with manual tranny.
For family use, this one!. No crazy mods on engine or suspension or drive train. Just nice audio and computer on board. More for occupants than driver. These days enjoying more Fun Runs with the BMWclub in Philippines. Still doing small mods occasionally. Can't help it when you got the Mod Bug!.
Couple of questions:1) Any particular model of MAF that I must go for? 2) What is piggy back? Why is it neccesary?3) How much should it cost?4) Anyone wif related experience you want to share on the pros and cons?Thanks in advance for the feedback. 
