I have a 2004 mini cooper S, a few years ago i bought the mini and put in Single mass flywheel,17% Supercharge pulley, Colder plugs, Arp head studs, Crank shaft pulley, a header and custom exhaust, a full engine and head rebuild, and pretty all new sensors and seals, i bought a Byte Tronik full access tuner with 550cc injectors. Everything was running good for a few months drove around 11,000 miles did alot of hard pulls the A/F ratio was always good. then out of the blue over a week it was running worst and worst wouldn't idle and running really rich got a 02 sensor code and replaced it with a NTK got the code to go away for the heater circuit then got a Tmap sensor code replaced it with a AutoZone brand and it still has a very hard start if i keep the petal about 50% i can keep it running but a lot of black smoke and short term is max rich. So i deicide to unplug the Tmap sensor and weird it idles and revs good i don't want to drive it with no Boost sensor but right when i plug the Tmap sensor in the car dies. I been reserching this problem for a month and cant find anything about it running good with Tmap Sensor unplug and dies right when its plugged in, Ive check the power and grounds the wiring and all seems to be good.

 

Fuel trims maxed out rich means the car has determined there is too much air or not enough fuel so it is adding fuel to correct either of those conditions.

Make sure no air leaks (intake or exhaust). Check for correct fuel pressure to the fuel rail. May as well check plugs/coil/wires too.

I'm not a fan of almost anything from AutoZone, especially sensors, so there's that. That tuner and big fuel injectors could make things tricky but check all the basics first.

 

You might want to touch base with Adrian Nastase (adriancl) on this forum. He knows everything about tuning R53s and can help you remotely.