IRL D4 S8 Valved Catback ExhaustS8 D4 systems are made to order 2 3 week production time. Our high performance Catback replaces the restrictive and heavy OEM system for improved flow increased power and sound without sacrificing drivability. Expect more aggressive tone from your S8. The IRL catback has no more restrictions and now you can expect to see an increase in 27 whp and 37 ft lbs of tq. Fits all Audi D4 S8 (2010 2017) Adds 27 whp and 37 ft lbs of tq Improved sound &