The SLS, according to Clarkson, has the most powerful naturally aspirated engine in the world. Anyone developed turbos or superchargers for these yet? It'd be completely ridiculous... but very PH
I think he missed 'production' and 'V8' from that sentence.
I am pretty sure the SLS engine is the worlds most powerful Naturally Aspirated V8 in production at the moment. (But I am sure someone will tell us different!)
As far as tuning goes, I recently read an article on a Brabus SLS. It was just a cosmetic and interior upgrade, but it referenced engine upgrades with a "watch this space" tone.
Shouldn't be long until one of the big tuners come up with some tasty engine upgrades