Whats the purpose of this thing, and is it going to mess with anything if I move my MAF to the pressure side without changing the tune or anything?

 

It's used to prevent high maf trouble codes on obdII cars. It won't care if the maf is on the low side or high side of the blower. Some say putting the maf on the high side improves throttle response. I've tried it both ways and couldn't tell a difference. The only risk I know of with putting it on the high side is that it could be destroyed if your blower grenades itself. I have never seen this happen though. Pretty sure it's just an urban legend.