[T3] 1600cc engine tuning

[Toadpipe]

I'm soon to be pulling out my engine to address an oil leak, I got to 
thinking about engine rebuilding.  I'm not planning to do this anytime 
soon but it raised some questions.  What sort of things can be done to 
tune the 1600 and get more power better performance?

The usual stuff comes to mind, counter weighted crank, ported heads but 
I'm guessing that ported heads on a D-Jet system would cause problems 
since it would alter the air density in the intake.  So I'm left not 
know what is even viable.  I'm also guessing that the lack of fan 
changes available would limit tuning as well.

Any ideas out there?  Yes, I'm hoping to keep the D-Jet as well as the 
85.5x69 diameter/stroke.

Toadpipe