https://forums.m3cutters.co.uk/thre...s-on-all-cylinders.214361/page-2#post-2839496 I had lots of replacement parts, duff o2 sensor, fuel cap, leaky injectors (one replaced, plus all seals on others), new plugs, terraclean (decarbon). The single biggest thing to influence it was the change of coil packs. I was lucky enough to be able to swap some parts around and rule out ecu issues. I even had boroscope checks on the cylinders etc. If you haven’t changed all of your coil packs it’s worth considering but expensive even from Cotswold bmw. I have seen broken valve springs mentioned before but if I remember rightly my mechanic thought it would be more regular an occurrence than I was experiencing. Good luck, I hope you sort it out!