You must keep in mind Cam timing and operating RPM.

You want everything to work together.
Huge intake passages deminish air speed and kill low and mid-range.

As far as the cam goes you could remone material off the back of the cam for more lift.

Your limiting factors would be:
Valve spring coil binding and Piston to valve clearance.

There is a lot of work involved doing these things.

I would start of with adding 15% nitro to my fuel.
You can pick some up at a go cart shop.
Remember always add nitro to gas, never gas to nitro.
A little gas in nitro is lets say unstable.