3" inlets, 2-1/2" outlets. Would you like a product that will give your pony additional horsepower, torque, reduced exhaust noise, and has been proven by the best to work? Have you noticed how the IROC Firebirds and several of the NASCAR race cars are sounding more like IndyCars these days? That’s because they are using the Dr. Gas Synchronizing Crossover Exhaust System! Since Sterling Marlin won the 1995 Daytona 500 with a Dr. Gas system on his car, many of the other NASCAR teams are using it also. And now, all of the IROC Firebirds use Dr. Gas! The reason is simple! The Dr. Gas Synchronizing Crossover Exhaust System is designed to work with any V6 or V8 exhaust system. Unlike other H and X designs, Dyno testing of the Dr. Gas Crossover shows a 1% to 5% gain in both torque and horsepower at all engine speeds over open headers! Also, Dr. Gas reduces exhaust noise levels by 2dba to 6dba! We’ve used Dr. Gas on both the #4 Grabber Green Fastback and #904 Grabber Green Coupe for the past 9 years and we can tell you from experience that it works! This mandral bent, 5 piece kit is a cut and weld to fit your application, and is available in a variety of sizes to fit almost any application. Sold per kit.