Changing the crossover up in the rpms by 1000 should make the vtec x-over more noticeable.

You may be having issues with weak spark considering you're poppin a code20. Did you use a conversion harness?

Check your ignition timing... when you say "tune up", what all does that entail to you? I'm asking because if you went all out and changed your timing belt as well, then you may have a slight timing issue.

-jonathan