This made in the USA system is the bargain of the century. Not only is the quality excellent, but it includes new high-flow catalytic converters! Expect an increase of about 20 horsepower and aggressive sound under acceleration but a mild tone at cruising speeds. (You might say it is tuned for the adult enthusiast.) For all XJ-S V-12, but we should note that the manufacturer has experienced some fitment problems with late convertibles with the factory under-floor bracing. Does not carry California CARB certification.