I've heard the TB helps a lot more if you match the intake manifold. Like if you buy a 62mm TB, you machine the intake manifold inlet to 62mm.

I don't think it gives you much power (no more than 5 or so) unless youre FI, or youve got a ported and polished head. But even so, the throttle response should be quicker, and generally big TBs level out the little dip in power just before the vtec changeover. I'm no expert, thats just what I've found out reading up and asking questions.