Also comparing the 48i to the 50i is not a fair comparison..
48i is a 350hp/350lb tq and does 0-60 in 7.2 seconds engine
35i is a 300hp/300lb tq and actually goes 0-60 in 6.4 (because of the turbo)
50i is a 400hp/450lb tq (twin turbo) and goes 0-60 in 5.3 seconds
If your planning to mod, go with the 48i or 50i... BUt your better off doing a comparison between the 35i X5 and the 50i 5 series... not the 48i... Just my opinion...
BMW X5 35i: Boopie Exhaust & Intercooler, K&N Drop in Filter, JB3 (3+ psi)
2013 Dodge Challenger R/T: CAI, Catch Can, Custom Exhaust, Headers, 87MM Throttle Body, Diablo Custom 93 OCT Tune