APR has a stainless steel, mandrel bent, cat-back
exhaust for the S4.
APR's S4 Exhaust is a stainless steel, mandrel
bent, cat-back exhaust. Our exhaust begins after the two lower factory
catalytic converters and is two 2.25" pipes that merge into
one 3" pipe. This exhaust is very quiet and simply changes
the tone of the exhaust to a deep, unobtrusive sound. With TIG welding,
fully stainless construction, and CNC'ed hangers, you will not find
a higher quality system on the market.
APR's S4 cat-back exhaust is available with two
different sound levels. The Stealth exhaust helps to maintain the
S4's subdued character. While louder than stock, it is not too loud
to attract attention. The SRT exhaust replaces the center muffler
with a special side resonator. This exhaust has a more aggressive
sound and a distinctive note.