I was thinking of doing the EVO upgrade as well but I held off for a few reasons. First off the stock air intake is a cold air intake. Look at the design. The snorkel tube pulls in completely fresh cold air away from the engine through the side inlet. The evo system actual sits inside the engine compartment where common sense would tell you air temps are higher. It takes in some warm engine compartment air despite the heat shield. Secondly, as you mentioned the filter can cause MAS problems probably due to the oil or sensor local. Many EVO owners say they have switched back due to annoying check engine lights and MAS problems. I've also heard from owners that the install can be pain due to the tight confines of the engine compartment. I've settled on something that works fine for me and probably gives you 3/4's of the sound and HP gain that the EVO gives. And I don't have to worry about any of the headaches like MAS problems and check engine lights plus it saved me some green. It's also a snap to install compared to EVO. Here's the link.
http://www.eagleday.com/pobmcpefi.html