By the time the hp gets to the wheels, intake and exhaust don't add very many horses. I don't THINK the Nur Spec fits the NA... and if it did I think it might be a little too much for the NA unless you are really pushing some power.
^ I have no idea. From the sounds of that original article it seems like a single. If you want a dual that fits a NA you can go with the Greddy SP. Thats what I have on my MR2T... it's not loud at all though.
There has never been a 5SFE (your engine) documented above 150rwhp.
Toms scoops do NOT give any performance gains whatsoever. In fact, because forcing air into the engine bay from the top disturbs air flow, you hurt cooling performance. (natural MR2 airflow sucks air from under the car into the bay).