Audio Upgrade to BMW Z4 2005. After listening to this car we realised why the customer wanted to upgrade the sound system. The customer opted for JL Audio speakers which consisted of VR525-CSi front components and VR690TX 6″ x 9″ speakers for the rear. The subwoofers used were Hertz Energy and these were placed into a custom built enclosure. Upgrade your 2004-2010 BMW E63/E64 645ci and 650i with high-performance bushings, bushings that won't cause vibration or noise and include a Lifetime Warranty! ... Brembo GT 380x34 2-Piece 8 Piston Black Drilled Front Big BMW E85 and E86, Z4 ser Projectμ. ... Brembo GT 380x34 2-Piece 8 Piston Black Drilled Front Big BMW E85 and E86, Z4 ser. Nothing else can come close to the boost in acceleration for the money. Costs range from $300 - $1900 for a differential depending on whether its salvage parts or new OEM. Installation is DIY to $300. A couple reasons it beats the other options are that the torque increase is so substantial and its everywhere from 1500 - redline. The BMW Z4 (E89 ) is the second generation of the BMW Z4 range of two-door roadsters, and was produced from 2009 to 2016.The E89 replaced the E85/E86 Z4 and is the fourth model in the BMW Z Series.. The E89 Z4 was the first Z Series model to use a retractable hardtop roof, which meant that there were no longer separate roadster and coupé versions of the car.