Was diagnosed by BMW main dealer cylinder 7 piston ring failure and no compression in cylinder 7, others seems fine. I know it's major task but in this case it's only 28000 miles so it's not that all engine worn out. Car was ECU tuned to 680bhp. I'm just thinking what parts most likely need to replace only piston ring or something else. Car is not much driven after this maybe 10 miles. I know if it was wear and tear it would be huge job and many parts need replacing. But this car is low mileage and I think other pistons and cylinders are fine. Of course tomorrow I go to mechanic independent specialist but today got offer to sell but for very low price just thinking if this could be few thousand job like 2-3 thousands or any case 10000+ job...?