What could cause my truck to run fine for 20-30 minutes then i lose oil pressure and the engine starts to make loud noises but it goes away if i hit the gas real hard.

Are you running the right oil? Is it at the proper level? Is the filter clogged?

If levels and grade of oil is right, remove the oil pickup tube and check for a blockage. The tube has a screen on the bottom to prevent large chunks of material collecting in the pan from being sucked into the oil pump. If it is clogged, replace the tube for about 50 bucks. You'll never clean out the tube completely.

i bought a new oil pump for what the tube cost, 2 stage air compressor seem to do just fine on cleaning them up, what is it clogged with? if its pieces of nylon it could be from plastic coated timing gears which i had once, if its metal you might need more than a pick up tube. i sure would be dumping the oil and looking at what was coming out. maybe fishing in the oil with a magnet. These new motors you might find chunks like the end of a crank sensor that the clown before you broke off and just knocked in the hole. can be kind of interesting. that was on a dodge 2 litre i pulled apart/