Is there any way to know if the intake manifold gasket is bad without removing the intake manifold?

 

Disconnect the intake hose into the air hat on top of the throttle body. Remove the air hat, hold open the throttle body blades and look down inside with a flash light to the belly pan gasket. A very light sheen of oil is normal, anything else and you've got a problem. Your oil consumption increases pretty dramatically, could be as much as one quart or more every 500 miles. You could also start pinging/detonating very easily under load. There is also a vacuum test that the dealer does but I'm unsure of the procedure. Somebody else chime in?

Hope this helps.