Newbie needs suggestions

Hello everyone! I recently bought a 99 GM w/46K and it has the performance and hadeling package and the only aftermarket is the original owner added a wider diameter exhaust and chrome tips. Don't know if this is stock or not. It's in "like new" condition and i love it! I would like to squeeze out a few more ponies or just enhance the performance without coprimising the gas milage big time. Advice? and thanks in advance.

Underdrive Pulley kit from MAC or STEEDA and a Trani Shift Kit.

3:55 gears if your feeling lucky. : )

Drop in a stock K & N air filter (p/n: 33-2272) for better breathing, which will help with the getup and go part. :-)