VF Engineering Supercharger System - 2001-2004 BMW 5-Series (525) vs VF Engineering Supercharger System - 2004-2006 BMW 3-Series (325)

Both kits are VF Engineering centrifugal Vortech systems at about 6 psi with VF ECU software, so the real choice is the car, not the kit. The 525 kit is the more complete package on paper: CNC aluminum bracket that keeps the OEM active-spring tensioner, molded polypropylene ducts, high-flow injectors, a DIY flash cable, OBD2 compliance and a one-year unlimited-mileage warranty. The 325 kit's standout is software depth: VF says it rewrote the Bosch and Siemens ECU code and fixed the stalling and MAF faults other kits had. Buy for the chassis you own; neither kit is a better design than the other.

• Choose the VF 525 kit if you have a 2001-2004 5-Series with the 2.5 six and want the kit with the machined bracket, molded ducts, injectors and a stated warranty.
• Choose the VF 325 kit if you have a 2004-2006 E46 325 and want VF's most heavily reworked ECU calibration, which targets the stalling and MAF problems other kits had.