MotorStorm: Pacific Rift Tips

Rear-ended push
Instead of pulling along side another vehicle and using the side boost to push them off course, try accelerating hard into the back of them aided by your boost. This causes them to lose control and often they will crash giving you room to move right infront.

The advantages of this are that it takes less boost to hit from hehind than it does to boost sideways using L1 or R1 and that when they crash they often go sideways into the wall, blocking cars from behind and giving you a clear lead.