I have all Dinan Stage 4 engine and transmission upgrades installed on a 2002 X5 4.6 that I purchased new. Upgrades were done over time starting at 10,000 miles. Made a huge difference. If you intend to make modifications step by step rather than all at once I would recommend free flow exhaust as the first step---for performance and a Great sound. Cold air intake will help some but without upgrading to a high flow air flow meter and high flow throttle body and engine software you can expect little more than it sounds better when pedal is on the metal.