Manifold Question

Hey 300m owners

I had my mechanic routinely check out my car a couple weeks ago and he noticed that the car shakes at times when idling. He suspects (and i agree) that this is due to the intake manifold on the car. The 300m has a dual manifold and he says that the lower portion is leaking. He says that this is a common problem among chryslers. Has anyone else experienced this problem? If the air/fuel mixture is off then that leads to poor fuel ecconomy. Im averaging 15.3 mpg. What kind of ecconomy are you guys seeing?

I just changed the upper and lower intake gaskets in my M for the same reason, however, it didn't make a difference. I'm suspecting a dirty injector or two. I have heard that the earlier 3.5's had intake issues...not sure if it's true. I drive mostly highway miles and average about 25 mpg. 15.3 seems low. I would guess my car would average about 17-18 in the city. I suppose it depends on how you drive. I'm a lead foot and still maintain average fuel mileage

I'm experiencing the same thing with the shaking during idle. I checked the motor mounts and it seems like the pass. side is kinda loose. I can move it about 3/4" in.