Hello fellow Mini owners! I need some help diagnosing a problem with my R56. I have a 2009 Cooper S with a Manic Stage 2 tune, and the car now sounds like a Subaru WRX when it tries to build boost. It starts fine, idles fine, cruises fine, and builds revs just fine as long as I don’t go past 25-30ish% throttle. That’s when the car begins to sound like a Subaru (real throaty sound with significantly reduced power). This makes me believe that the coils and internals are not damaged.

I have had the tune for around 5,000 miles, and drive it very easy on most days. Oil is checked and changed regularly. Valves were walnut blasted around 10k miles ago, and I did install an oil catch can afterwards.

I was doing a pretty hard highway pull when this problem occurred, and I was running 1.4 bar of boost (20.3 PSI). However, I’ve never had a single hiccup from this car as of yet. I checked for codes, but nothing came up. For a few months before this, I started receiving intermittent warnings for an open fuel cap, but it’s always closed.. unsure if that is related to this issue.

My guess is either turbo related (as in boost leak, or perhaps damaged wastegate) or dying fuel pump? I will take a closer look at the car this week to figure it out, but does anyone have any ideas / experience with something like this? Thanks!

Thank you! I’ll start there. Don’t have the spark plugs, but I’ll check the plugs anyways. If I can’t find any loose hose clamps / hoses, I’ll pull the DP and check the wastegate. If it’s bad, she’s getting one of those hybrid turbos and colder plugs

We ran some tests today. Turbo is building boost and the wastegate is not stuck open. Ruled out the oil catch can, coils, plugs, and boost leak. It feels, sounds, and smells like the car is running rich. Could it be a valve problem?