Need power

I Have a 97 f-150 with a six cylinder 4 speed man with OD. It's a work truck that has been well maintained but can't keep up to the big boys. I often have to shif down to third on moderate hills without any load on. Any ideas on how to boost the power without changing gear ratios or motors?

Put on headers and aftermarket exhaust and you will see a big change. You can also increase the air into the fuel system for just a little more pep.