[HUMMERcustoms.com/TAZ]

Find a local tuning shop or contact Allen Nelson at Nelson Performance to put as lean a tune as safe a tune on your stock setup with you adding a cold air intake to the mix. Switch to a top quality synthetic engine oil and any other fluids you can change. I use all Royal Purple as I saw Horse Power TV on Powerblock do a actual dyno run in a latish model Camaro using dino oil first then changing to Royal Purple engine oil gaining 8 HP. If motor can gain HP on oil change only, it means friction was reduced so MPG must be helped some. Thus changing to all syn oils any place in ride you can will only help HP and MPG.

The leaner tune will gain you roughly 40 HP and use less fuel while it does it improving MPG. So just maximizing your stock engine anyplace you can is the cheapest and easiest thing you can do to help yourself. Basicly this is what a handheld tuner does for stock rides but, even their tunes leave up to 40 HP on the table over a custom tune job.

Allen can offer other suggestions if you contact him for a tune. You can go to a 160 degree T-stat will help. Go to electric cooling fans in place of your mechanical fan and gain 18HP.

Hope this gets you going in right direction. Oh if you start lifting the rig and adding bigger tires and rims it will use any gains mentioned above. You could with HP gains go to 3.65 gearing or something versus stock 4.10 gearing to get you into a lower RPM range quicker.

You could gain up to as much as 75 to 100 HP without SC or turbo etc.
I know I gained 125HP at wheels after all my mad scientist stuff. Every engine or rig is different. I know it appears right up front I got a ride that responed really well to every adjustment I made to it.

TAZ