More air = more power. Simple as that. The stock bmw HFM's suck on some bimmers. I am planning to get that kit too, it does alot.
Current standings: 98 M3 Track car
Mods: suspension, i/e/fly only
1/4th mile: 13.7@101 on 235/40 streets
Rd Atlanta: 1:44's on RA1's, 1:46 st.trs
95 M3 3.2obd1