hell even simple things like changing over to full synthetic oil having the proper air pressure in the tires and a tonneau cover can do quite a bit.
Im personaly working on my truck so that I can use it to pull my car around when ever I get it done Ive been doing simple maintenance things like plugs, wires, cap and rotor, replaced all the hoses, and just recently had the intake gasket replaced. most of that stuff probably didnt gain me anything but it seems like the gasket did gain me some power probably because the truck isnt trying to burn coolent and a bit of oil anymore