hey guys so i have a 2005 ba xr6 na auto, only have 2 or so years left on my p plates and then i plan on going onto a bf turbo or maybe even an fg manual turbo anyway........

the car has been fitted with hi flow cat, pacemakers 4400's and 2 1/2" catback system from redback it also now has a big mouth from ss inductions and a K&N panel filter.
Ive read around some people say its worth getting 20% underdrive pulleys, would it be worth me getting the under drive pulleys and a tune or am i not gonna see any gains at all and am wasting money on nothing, i know its hard to get power out of a na but until i get a turbo this is all ive got for another 2 years, i just want it to have more low end torque and mid range power.

Thanks guys for your help in advance Nick

as well as a bit quicker on the throttle response

Yes tune it under drives and some 4.10 diff gears and you will be happy with it. B series N/A make very good power with the right tweaks