Welcome Aboard!! There are alot of things you can do for not alot of money. I would definately start with 4" exhaust and then maybe a tuner or intake. Although the factory intake is fairly good, if your going with a tuner, IMO I would change the intake also. 
__________________ HAD - 94 Chevy Dually 4x4 - 6.5 Turbo
96 Chevy Ext.cab 4x4 - 6.5 Turbo
99 GMC Dually 4x4 - 6.5 Turbo
HAVE - 2005 GMC Sierra crew/6'box - 4X4 - Duramax w/Allison. Fully loaded - AiRaid intake - 4" Pinnicle Performance Exhaust (No Converter - Straight through muffler) - EGR blocker plate - Edge Juice w/attitude - 2" plug in Turbo Resinator - |