A comparison between the Banks and stock turbine housings doesn’t reveal any differences. That’s because all the differences are on the inside. The Banks housing has a larger inside diameter, which creates more room around the impeller, allowing more exhaust gas to fit into the turbine chamber. Since we’ve forced more air through the intake side and into the combustion chamber, when the exhaust valve opens, all that extra air wants out. The stock turbine housing is too small to handle this extra air and backpressure builds up, causing excessive exhaust gas temperature, which inhibits the power potential. With the bigger Banks housing, the air can pass quickly over the turbine blades, spin the turbo, then dump into the equally free-flowing 4-inch exhaust pipe for a trip to the back of the truck.