You can get a VTEC head (epx has 2, if you'll looking for one). Should give you somewhere around 10-15 horse with no other modifications. The other 10 horse would come along with a VTEC intake manifold, VTEC style header instead of the close coupled cat, etc.

It isn't easy to install but not difficult either. You'll need to properly seat a headgasket and do some wiring.

You'll need a VTEC ECU, yes.

Venom 400 is totally worthless, don't even waste your money.