One of the very best upgrades I applied to my '04 MSM was a proper intake. Somewhere floating around are dyno sheets of the same car, on the same rollers, on the same day doing back-to-back runs of stock intake vs aftermarket "CAI". I'm not sure if the "C" was actually correct, but my CARB-approved replacement was worth something nearing 20whp.

I wasn't able to modify exhaust because Communist Republic of California, but a DP + full exhaust is worth easily another 20whp. Add a few more pounds of manifold pressure, get the tune right, and you'll have smiles for miles.