Thread: annoying thumping sound at firewall idling in gear

Yes, it is where the DP bolts to the rear manifold and they are tight and nothing leaks.I think I know what is making the DP rattle, the engine vibrates at an idle just enough to make the inside of the car rubble and make the plastic rattle.It's not a miss, I dont think, it runs perfect otherwise.With my foot on the brake and the other on the throttle it never really stops vibrating till around 1100 rpms and then it slowly smooths out. I have sprayed the entire top of the engine with carb cleaner to see if it has a vacuum leak but have not found anything.The plugs and wires are all new.I cant think of what else would cause a vibration like that. Could there be a vacuum leak elsewhere or do you think its something else?