On my VY V6 series 1 the only performance upgrades I have is a 2.5" catback exhaust. I am currently looking for a little more punch and throttle response .Can you suggest some basic engine modifications at a reasonable price. Which combinations work the b

If you were solely after improving throttle response and torque down-low, then I would recommend a 25mm manifold insulator, a 69mm throttle body, and a tune to suit. Otherwise, other performance upgrades to consider are shown in the link below:

http://support.maceengineering.com.au/Knowledgebase/List/Index/129/v6-ecotec-performance-packs

If you’re planning on getting a larger throttle body and have an automatic VY V6, then it would be recommended that your computer/PCM is reprogrammed to suit. Otherwise, if you’re considering additional modifications after the initial ones then hold off tuning your vehicle until you’re satisfied with the modifications. Furthermore, it is not necessary to tune your vehicle with small modifications such as bolt-on packages (excluding the throttle body on an auto vehicle) unless you would like to further refine and increase vehicle performance.