Another weird noise?

ii got a 93 f150 5sd 4x4 4.9l. i got another weird noise.i was driving today and i heard a sand paper type noise coming from my truck. when i would push the clutch in or put it in nutral and give it gas i would not hear the noise. but when it is in gear and i give it gas i hear the sandpaper type noise. could this be u-joints to? or could it be the A.I.R. injection pipe that goes in after the cat. i the pipe had rusted off so i did a cheep fix on it. but would i hear that noise if it was the air injection pipe if i put the truck in nutral?

it was exhaust

I figured it out! Either your radio doesn't work or was recently stolen.