APR Catback Exhaust System (Valveless) MK7 Golf R Railway overhead electrification system design Civil Engineering Tech. The APR Catback Exhaust System personalizes your vehicle's looks, sound and performance. Beautifully hand crafted T304 stainless steel components adorn the system with stunning TIG welding throughout. Our straight through brushed finished stainless steel piping give the exhaust note an aggressive growl without any restrictions, while our Helmholtz resonator reduces unwanted frequencies. Strong high quality bracketry and OEM style clamps hold the system steadily in place, making the install or removal a snap, and fitment simple, yet precise. A cast 3" to quad 2. 5" rear splitter creates an ultra smooth transition, steadily feeding exhaust gasses out of the system, while looking tidy from under the rear bumper. Lastly removable 4" polished slash cut exhaust tips finish the system, adding a classy motorsport inspired touch to the rear of the vehicle. For the more track minded enthusiasts where weight, sound and price point all are highly desired metrics, the APR Valveless system is the desired configuration. In this configuration the axle back portion of the exhaust has the mufflers and valves removed. Weight drops considerably and the system becomes more aggressive. With the factory DP in place, the system is louder and more aggressive, but thanks to the center Helmholtz chamber, drone is reduced, giving a more pleasant, yet aggressive driving experience. However, when upgrading to the APR Race DP, the system transforms and becomes unapologetically raw with maximum aggression A true track enthusiast's dream.