2000 GMC Sierra Loud Ticking

[Bradamoki]

Hello I have a 2000 GMC Sierra 5.3 4x4, it has been sitting for 6 months. First thing I did was change the oil, next I drained the old gas and put new gas in. The truck would crank but not turn over. I replaced the fuel filter, and replaced the fuel regulator. Prior to replacing the fuel regulator I had no fuel pressure, gas was leaking through the diaphragm of the regulator into the intake manifold. Once I replaced the above items fuel pressure was up to 50psi with key in start position. The truck fired right up no problem but, there was a very loud ticking sound that sped up and got louder when I pushed on the gas. I immediately shut it off. I checked the oil and the dipstick smelled like gas. I drained the oil and there was a lot of gas mixed in with the new oil. I replaced the oil filter and filled it with new 5W-30 Mobile 1 high mileage synthetic oil. It fired right up again and the loud ticking sound was still there. Oil pressure was good I let it idle for a few minutes and the ticking got a little bit quieter but, still loud. Check engine light was on and the codes were P0300 and P0200. I hooked up a Noid light to each injectors wiring harness at idle and every one was firing. I removed the fuel injectors and cleaned them, did OHM test on each one and all of them had consistent readings. I do not know what else to do from here? Any help, direction, or advice would be greatly appreciated. Thank you for taking the time to read this.

My truck has 245,000 miles on the original engine.