It's a hotwire system so it measures the air going passed it and spits out a voltage. Problem is you get up to around 500hp (IIRC) and it tops out, the signal voltage hits a max at 5v (IIRC). So you split the air into two paths, average the signals instead of adding them together (so your voltage signal is half the air coming in) and that gets you a 1000hp worth of air measuring, far above anything most people will need. That does require that you alter the fuel maps (double them to account for only measuring half the air) and so eventually you'd need a dual MAF ECU no matter what kit you use to run the sensors.
