Big Gun Exhaust Systems EVO R Slip-On , Material: Aluminum The Big Gun Evo Racing Series was designed to deliver maximum horsepower and torque gains throughout the RPM range. Made from .049 stainless steel tubing and an aluminum muffler canister, the Evo exhaust system is much lighter than stock units. Our sleek muffler design also allows for maximum clearance to avoid your exhaust from hitting the rear brake caliper. 4-8 horsepower increase on most models. 96-98dbs track and trail legal (with Vortex insert sold separately).