Cosworth made some engine parts for ///M Gmbh for their Gruppe' A cars. Trust me, these are not cheap parts unless you have great contacts/relatives in the industry... And yes, with that high compression you'd have to use high octane fuel, might get away with 100 unleaded. Either way that's quite expensive, much more so then your simple Turner Motorsports 2.5 upgrade..(which I am sure will offer just as much or maybe more torque then that 2.01 (??) liter. Sure, those 2 liter touring E30 M3s were great, but that is NOT AT ALL practical for a street/weekend track car or even club race car unless you've got a massive budget to accomodate the car...