p0300 and mass airflow sensor
 

Ok...Hopefully someone will be able to help. I have been getting p0300 codes coming up on '01 Chevy Express 3500 (5.7 litre) over the last week. It only throws the codes while I'm idling. I have checked and repaired a couple vacuum lines, cleaned the mass air flow sensor, cleaned the throttle body, installed new plugs cap and rotor, ran fuel injector cleaner through the fuel system, checked the for intake manifold leaks, etc., etc,. Today I decided to pull the plug on the maf sensor, all of my misfires dissapeared and my van was running great. Since I figured that was the issue, I bought a new maf sensor and installed it, cleared the maf code and started it up. Not even a minute later, it started throwing p0300 codes again. I unplugged the new one and the misfires vanished. Has anyone had any similar experience? I'm at a loss, and don't want to just throw money at it. Thanks in advance