Fleece Performance 17-22 GM 2500/3500 Duramax MAP Sensor Spacer & Boost Reference PortFleece Performance MAP Sensor Spacer with Boost Reference Port for the L5P Duramax. Problem: Because of the direct placement of the MAP sensor into the intake air stream from the factory, soot buildup becomes an ongoing problem. This requires the sensor to be routinely cleaned or replaced. Solution: The Fleece Performance MAP sensor spacer moves the sensor from the direct intake air stream to reduce soot buildup over time and eliminate the need to