There are owners of SLK 320s out there (same engine exactly) that have these upgrades done, so that is how they know the mods will work. The mods that are a little different for the Crossfire, like a carbon-fiber air intake, lowering springs, and exhaust are not yet available for the Crossfire, and I'm not sure if and when they will be available. And as for reliability, there are a lot of RENNtech modded cars on the road, and the founder was the technical director of AMG and worked for AMG for over 12 years, so he knows pretty well what he is doing.