Before those exhaust gases completely escape down the exhaust pipe, they first pass by the wastegate. This unit acts like a trap door and stays closed unless pressure becomes too great within the turbine housing, or the engine is in warm-up mode and the computer doesn’t allow it to receive a lot of boost. When this happens, the wastegate door is opened by the actuator on the left, allowing the exhaust to bypass the turbo and go straight down the tailpipe. The Banks Big Head actuator on the right replaces the stock unit. The Big Head is calibrated for the changes made in turbine pressure by the new turbine housing. It maintains more boost throughout the powerband while making sure there is no over-boost.