Recently Installed JB Stage 1 in X3
I just installed JB Stage 1 for my X3 35i over the weekend, so far just on standard boost of 3.5 above stock, some appear to have success closer to 4-4.5 with 93 octane. So far only good things to report, gas mileage appears to be in same ballbark as before, power is much improved over stock particularly in sport mode. Pulls much harder from a stop as well. For the money, its a worthy hour project, probably 20 minutes after its been done once. I will say the instructutions don't really match the reality of the new X3. The 3rd sensor (MAF) I believe is connected to airtube instead of sitting on top of engine cover as described, so you have to take off tube and cover to get to and then there is no plastic box to put the JB into once you are done so you've got to secure it yourself. Pretty easy work arounds, but just an FYI for would be installers. Take off airbox and the job is I'd say a 3/10 in terms of ease of install; 1 being easiest.
'13 X3 35i Msport | Silverstone/Oyster/Aluminum Trim | JB Stage 1
'08 135i coupe l SGM l Step | Quaife LSD | Cobb Stage 1