How can I increase the power of my 2006 silverado

Cheap and easy. Get a program for the computer (ECU)

How much money do you have? How much money are you willing to spend? What kind and how much power do you want? Do you care about mileage? Start with a cold air induction. Headers run around $250 for good custom fit headers. Low restriction cats, are a bit of change, larger exhaust stainless steel exhaust pipes are a must to mount the non-restrictive mufflers. That alone will be around $500. Larger injectors, different runners, or go with a newer custom EFI set up, for around $4,000, or change the EFI command module and ignition set up. Different cam, high flow heads, larger fuel pump, Edelbrock blower and set up, or turbo kit. Between $5 to $10 Grand will get you all the power you need to pull stumps. Change out transmission and rear end. Tires and rims. It all goes into getting more power, but it also costs money, especially if you go with the top end items which are most reliable. Do all this and you'll have so much power your gas credit card people will love you.