Porting your head will just allow more and a better air flow, and i think it you have a gt inlet manifold its worth it, or get it port matched. Having bigger valves can help as well but its more money and not much more power gain.
I recently had my head ported my man in shed and it was brilliant. Wouldn't take it anywhere else.
I also had my bottom end bored and wossner pistons put in and i think its worth it really. Keep the same compression ratio and got a stronger bottom end now.
Having all that work done would prob gain 15-20bhp depending on its map as well.
Mine was 149 before the work and i haven't put it on a rolling road yet. Was predicted about 170-180bhp but only a decent rr will tell.
