It's not quite just a built engine. I just didn't have enough room to write everything in my sig. The engine I have in my car is a Remanufactured S50 engine From Bavarian Auto Recycling, with the performance upgrade. Here's what they say about it on their site, and it really is not cheap.
If you're looking to get more power out of your BMW, then upgrade to our Performance Option and increase your horsepower by 20%. This option provides a substantial increase in performance while preserving the 5 year warranty, factory longevity, and emission standards. The upgrade includes flow-tested CNC cylinder head porting & hand polishing, Bavarian Performance camshaft, MaxSil pistons with Tefcote, Sealed Power piston rings, and precision balancing. Proprietary Bavarian CNC porting provides optimized turbulence, maximum air flow and precision consistency between ports. Click here for details on precision porting services by Bavarian Engine Exchange.