Underdrive pullies do help. They are a good bang for the buck. But, I would recommend you upgrade the charging and cooling systems before adding underdrive pullies. That depends on what year your car is though. Forget the chip too. It's not going to do anything for you until you actually need to chip after moderate modifications.
If you click on the image in my signature and go to my site click on the Tech link. I have an article there called The Basics just for topics like this. The direct link is here...
http://www.indianastangers.com/2FastLX/tech/basics.htm
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