how do I pick what size maf to get

I am of the opinion that it is better to get the smallest MAF you can that will flow the amount you think you will flow. The reason is that, the larger the maf, the larger the granularity, which means that the difference in the amount of air represented by 2 adjacent voltages from the MAF is larger on a larger MAF than it is on a smaller MAF. This results in the computer having a harder time really knowing just how much air is coming in, which can result in less accurate injector pulsewidths and load calculations.

At least, that is my opinion.

That said, with a supercharger, something along the lines of a 90mm LMAF would probably be a good choice. Either that, or one of those new MAFs with multiple sensor elements that are supposed to give a very accurate reading.

As to calibrating the MAF for the injectors. While it is better to have them so they can work together without a tune, a supercharged application really should be tuned because of the way the timing curves and load calculations should be tweaked for a forced induction setup. Having them calibrated so they can work together really only buys you the ability to start the car and limp home should the computer decide to go into safe mode for some reason and the tune is lost. It also allows you to drive it to the tuner for the initial tune.

Again, just some opinions from a random guy on the internet.

what he said....either the lightning or a prom 80mm (what i use).