Jack – Don’t buy a downpipe unless the company delivers a HP improve estimate in addition to a dyno chart. Even so, as soon as the N54 warms up the downpipes are rarely obvious. Idle inside the auto will seem inventory. Moderate cruising and driving will lead to OE-like Seems https://catlessvscatteddownpipe86420.jasperwiki.com/6037034/not_known_details_about_catless_vs_catted_downpipe