The intake manifold is a pretty damn good, in fact it has the longest designed runners in the industry.

I haven't had the privilege to examine the 112 cylinder head, actually porting the head and adding larger valves could easily bring up the power output to 10 hp/cylinder, maybe more if done in conjunction with bumping the CR up another point or two. You can easily get the little 3.2 L to put out 300 hp.

After that I would start looking into a big bore piston kit. I know LA-Sleeve makes high quality cast iron sleeves to any dimension you like. Here is their website: http://lasleeve.com/master.html

Actually now that I think about it, making a big bore kit would probably be an easier place to start making horsepower vs. porting and valves.