Magwah

New truck to me, been driving really soild until recently. 1996 4cyl 5-spd with 180,000, just drove from WA to MT picked up a sled then drove it back to WA over 2 snowy mountain passes and the truck had enough power a drove well until I stopped for gas 40 from my house. Since then when I accelerate there is a strong clicking sound from the engine area directly infront of the driver that increases as the need for power increases. No sound when idling or when in gear without the gas pedal engaged and there is no loss of power or any other issues other than the terrible sound . If it was the timing chain wouldn't the sound be the opposite as in the sound would increase as you decrease rpms? What could be going on?