there is a ton of work in there if you know what your looking at. things like port and blowdown timing, crank timing, squish band, head clearence, compression ratio etc (i really have no idea what i am talking about lol) it will be hard for someone to see unless they know what they are looking at. But things like lightened piston and rod, sluged and filled crank are plain as day. so basically, everything on that engine has been moddified. All the ports, crank, P/S and head button. Possibly even case volume. Now days most engines come with optimal air flow. It's all about timing with neil. And what a DIFFERENCE it makes!!!!

I often wonder though, if a modder can get this more performance by adjusting the timing, why don't engine manufactures do this to begin with?