Thought I would put some comparisons up with dyno charts. Rob Levinson sent me the orginal dyno comparo and I updated it with my latest dyno run.

The dark blue is an E39 ///M5, the 4 lines together w/red,blue,black,purple are Rob Levinsons 3.8l JimC tuned E34 ///M5 Touring, green,black are my old dyno runs @11psi and lots wrong with the system, and the red is my '88 535is Dinan Turbo Final Edition @ 14psi

As you can see, the area under the curve tells alot why ///M5 engines are really good and have "lots of area under the curve". This wide power band make them really fast and smooth. Especially the E39 ///M5, its got tons of torque from 2k to 7k. Both ///Ms have 4v/cyl filling and carry a really flat torque curve for a large power band. Compared to the 2v/cyl turbo engine, it looks very peaky by comparison. This tells me why BMW has strived very hard to stay away from turbo engines........