the truck runs and sound good when driving but soon as i take my foot off the gas it sound like a misfire but no code or leaks in the exhaust I put my hand over it it plow my hand off and also when in park I give it the gas trying to keep the rpm at 1k every time the exhaust sounds like puff of air the rpm will drop then back up, took all the plugs out to change them but all look brand new so i change them anyway did the compression all was around 120psi planning on putting a x-pipe to see if it helps also I have mid headers straight to the mufflers all this happens on the passenger side only.

 

update i got obd2 scan when i start the truck both upstream o2 sensor reads good on the graph but after 30sec or so as soon as the truck start to sound like misfire both o2 flat line it was .0something for 4-5sec then .9something for 4-5sec and so on so I thing the o2 are bad got some on the way so I unplug both o2 the truck runs the same, even same mpg which is 16mpg nothing change.