What's the secret behind Pathfinder power? Something we call VQ technology, which combines the use of precious metals, lightweight materials and race-bred engineering. An aluminum engine block, cylinder heads, and pistons add up to light weight and superior strength. Friction-reducing measures include molybdenum-coated pistons and a microfinished crank and crankshafts, both of which help the engine operate more smoothly and last longer. And double platinum-tipped spark plugs help Pathfinder go 100,000 miles without a tune-up.
Click on 'Variable Intake, Variable Valve', it says:
Breathing is everything. Anyone with a trained voice or a Nissan engineer will tell you it's the secret to power and range. For example, Pathfinder's Variable Intake System automatically changes how air flows through the manifold according to engine speed. You get plenty of thrust off the line; then, as rpm rise, it opens a shorter air path in the manifold for a more direct pipeline to power. Continuous Valve Timing Control similarly changes engine "breathing" according to conditions. It precisely modulates when intake valves open and close, factoring in throttle position, vehicle speed and engine rpm. Again, the result is outstanding low-rev acceleration, with deep reserves of passing power.
I am pretty sure that the QX4 and the Pathfinder are mechanically the same, i.e. engine, brakes, etc. The QX4 just has more luxurious amenities than the PF to justify the difference in price. But both are exceptional vehicles.