will not idle with aircleaner removed

99 yukon 5.7 vortec. will not idle with aircleaner removed. idles ok with it on. problem or not?? seems like it ran before with it off. mpg sucks worse than normal. slight hesatation cruising at highway speeds. check engine light not on.

anybody have any ideas??

Yup suppose to be like that Its a vacuum thing with those motors not sure of the tech of it all but have been around them enough to know for sure it's normal operation. Maybe try the fuel filter?? sounds like that could be it or tune it up plugs,wires,etc