A couple of things Id recommend on every Dmax (and one for LB7).
LB7: Boost Increase Valve: The boost increase valve was specifically designed for 2001 through 2004 Duramax LB7 diesel engines and increases boost pressure from 18-20 PSI to 28-30 PSI for additional horsepower. Totally safe for stock engines and turbos.
Tie Rod Sleeves: Tie rod sleeves go over your OEM tie rods on your steering system for added performance and strength. Dont bend a tie rod playing offroad, or sledpulling or racing! Its cheap insurance from ruining your day and sending you home on the back of a flatbed!
Pitman/Idler Arm Support Kit: Takes the slop out of your steering and supports the pitman and idler arm for offroad or racing/pulling use. Even if you just plan to go to a slightly bigger tire from stock, it can wear out your pitman/idler arms which are hundreds of dollars to replace each!
Its a simple install and REALLY tightens up your steering feel.
From there on you can get into more power adders, such as a fuel lift pump, plug in tuner and more.
Let me know if youd like pricing on any of this stuff or more info. Thanks and congrats on being a new DMax owner! I remember the first day of my first dmax...