So with a ported factory blower, we're again getting more power than expected. As Lauzardo mentioned, there have been several instances where other people have made over 500 rwhp from the identical setup, but with the stock exhaust manifolds, throttle body, and inlet pipe, we would not see the big five-double-0. In reality, it doesn't bother us because the car is just plain nasty on the street with First gear being literally useless with so much torque and traction being a huge issue in Second. Hooray for neck-snapping grunt. The problem is, now it has us wanting more.
Pulleyed For Max GripOn all '03-'04 Cobras, adding an underdrive supercharger pulley increases boost. That's fine and dandy, and yes you get more power. However, one of the biggest issues with this simple mod is the lack of adequate belt wrap with the reduced diameter pulley. It can cause slippage, especially when you're powershifting. The best way to tackle this is to use an auxiliary idler pulley right next to the supercharger's snout to provide the additional belt wrap. What does this do? Well, it makes the belt have more contact area with the pulley and it greatly prevents slippage to make sure that you get the most amount of boost possible with your setup.
For our car, we went with Steeda's billet aluminum setup, which not only looks the part, but also plays the part with a 100mm idler pulley diameter. It bolts right to the factory supercharger "bridge" and installs in mere minutes. Because the belt now has a new route, it will require a longer belt, typically one-half to a full inch longer. If you are using a stock crank pulley and a 3.0 upper, you'll need a Gates PN K080745. If you are going to a four-pound pulley like we did with the ported Eaton, then you will need Gates PN K080850. With your belt tensioner nice and tight, before you know it, you'll be rewarded with slip-free fun.