Engine Knocking nosie after replaced upper intake manifold

I just replaced the upper intake manifold on my 2004 mustang gt. I drained the radiator before I started to take it apart. All hole were covered after it was taken out. The new intake manifold came In the next day. I put it on and hooked everything up and now has a loud metal noise when it starts up. It has never done it before. The car starts no problem better than it did before. I it off instantly once I heard the noise. I took off the new intake manifold and checked to make sure nothing gotten down into the engine. I replaced all the plugs and coils and it is still making the noise. Any ideas? The car ran perfectly up until the new upper intake manifold was put on

It was the upper intake manifold that sits on top of the engine under the throttle body. No other work was done to the car at that time. As far as I no nothing was spilled when the old one came off I made sure of it. But I am changing the oil today in the safe side. And I'm not sure how