93 idi making funny grinding sound

[killer IDI]

hey i need some input, my truck has recently starting making a grinding noise in front of the motor, it only does it at idle but stops when you hit the gas pedal in. it only has 85k miles but i did turn the fuel pump up 1 full turn. could the timing be out, or is it something worse like crank bearing or a thrown rod, like i said its not a consistent sound only happens when i hit the breaks and when im sitting at idle or then that you dont hear it... plz help