aFe 49-03065-B ATLAS 4 IN Aluminized Steel DPF-Back Exhaust SystemaFe 49 03065 B ATLAS 4 IN Aluminized Steel DPF Back Exhaust System Flow and Performance: This ATLAS exhaust system is 100% hand MIG welded and Constructed from 4" mandrel bent aluminized steel tubing for maximum flow. The smooth transition bends allow for low turbulence, increasing horsepower, torque and lowering EGT's. A mitered merge collector is also incorporated to eliminate dead space that can cause turbulence and hinder flow. Intercooling