my 2004 f150 truck has a rough idle. I followed your suggestions about checking the cvt solenoids, fuel filter and maf sensor to no avail. so I removed the air box to listen for vacuum leaks and heard some but could locate it. So i covered the throttle body opening completely and to my surprise the engine kept running, idled better even with the maf unplugged and could still hear air sucking somewhere. Any suggestions, opinions or comments? Thanks

 

Use an unlit propane torch to find the vacuum leak - you will need a scanner in the OBD2 port, when the propane finds the leak the fuel trims will go nuts.