I have noticed lately that my truck has a slight rattle knock type noise that you can hear right around 2500 rpm. My truck is a 5 speed 4.6 and only seems to mainly do it taking off in 2nd gear. It doesn't seem to do it in any of the other gears. I only have 129K on the truck. My truck is bone stock. I recently changed the spark plugs and cleaned throttle body and the egr ports. any ideas on what this noise maybe? Thanks

 

Put some premium gas in it and see if it goes away.