I've done it to my car. I'm using the Stett stage II and it works fine. My track temps were almost 315C and now they're 270-280C. Water temps were never an issue (until the head gasket started leaking). The oil can survive 300C+ but it breaks down really fast. I think the car will cut power at 350C but I'm not too sure about that.
'06 Arctic Metallic 325i | Sport Package | 6MT | Dinan Stage III suspension | Dinan exhaust | 330i manifold swap! Click here!
| Active Autowerke tune | 135i Brake Calipers | Deiselboost caliper brackets | E46 M3 front rotors