Solid modification which is easy to install, nicely designed, and with clear instructions. Modification produced good results with improved performance and improved gas mileage. No peer.
Good modification with well written instructions. Intake and shark program produces a very noticeable improvement in acceleration, derivability, and economy. Vehicle produces a very nice rumble at WOT. Much easier to drive hard and shift by sound vs looking at the Tach. The looks of the Dinan is more attractive however and I'm not full comfortable with the foam filtration system. I am more familiar with the traditional K&N filtration mesh and this foam will take some getting used to.
Both recommended. Very nice improvement. A little hard to stomach that BMW left so much on the table on their flag ship sports car.
U/D pulley. Purchased from ERT for $350.
Product seems over priced for the materials received. The instructions were poorly written without much effort or thought. Performance improvement was negligible. Took 4 hours to install. Complete removal of radiator and water pump needed to install correctly. May have to shim unit to get it to align. (I did). Unit takes different belt so be sure to get part number written down in owner's manual. Unit eliminates the harmonic balancer which may or may not effect long term durability. (BMW puts this mass there for a reason). The actual diameter difference is about an inch. The mass removal has the most impact.
Not recommended. May compromise the integrity of the engine. Costly and requires time to install. Can remove the rear tire in 1 minute with no money invested and get similar gains. Will remove.