120 Nm,
For your 2006 BMW 330I: Wheel Stud Torque 72-87 Foot pounds (Final torque)
The x stands for BMW's four wheel drive system (called the x-drive) which they also use in the X5 (4 by 4) and X3 (SUV). Thus it simply indicates that the 335Xi is four wheel drive vehicle. It's a very nice car as well.
Because there is something wrong with it.
The 2006 BMW X5 has all wheel drive.
The 2006 BMW M5 has rear wheel drive.
The 2006 BMW X3 has all wheel drive.
The 2006 BMW M6 has rear wheel drive.
The 2006 BMW Z4 has rear wheel drive.
The 2006 BMW M3 has rear wheel drive.
The 2006 BMW X5 has a 9 ft. 3 in. (111 in.) wheel base.
The 2006 BMW Z4 has a 8 ft. 2.2 in. (98.2 in.) wheel base.
The 2006 BMW M5 has a 9 ft. 5.7 in. (113.7 in.) wheel base.