Keep in mind that if you are using a blow off valve which blows off to the atmosphere (i.e. doesn't recirculate the air back in the pipes) then you will end up runing really rich. Essentially this set up messes with the MAF and you end up with backfiring, poor gas mileage, and fowled spark plugs.
There are a couple good ways to get around this and still keep the blow off to atmosphere sound. I relocated my MAF to just before the throttle body (search "MAF relocation") and the car runs like a top now.
And yes, I do still recommend an aftermarket a/f computer of some kind to tune the crappy MSP factory tune (that's recommended if you have no mods b/c of the factory MSP tune being so poor).