1994 Silverado 5.7L engine torque

I haul a trailer over the summer and my truck runs a 5.7L GM gas engine. You know what THAT means - lousy fuel mileage and expensive trips! I note that when I am facing any wind above 5 km/hr the gas mileage gets worse and worse the grater the wind as a result of what apparently is a gas engine's inability to generate sufficient torque at higher speeds. I've considered buying a diesel, but I can't afford to pay the $10,000 more that they cost. Is there anyone out there that has found any solutions to the problem of torque, gas mileage, etc. when pulling a trailer? I've thought of trying a wind deflector on the cab but I pull a regular travel trailer and was advised by a truck shop salesperson that they have almost no effect on a travel trailer - they are designed apparently more for a fifth wheel.