Exhaust coming from under hood

[OUMX117]

Hey guys I just noticed this problem the other day when I was working on my truck. Whenever you rev the motor up there is a small stream of black exhaust that shoots from the top of the motor towards the front of the engine. The stream comes out somewhere near the fuel bowl. Any ideas on what might be leaking under there? I was thinking up-pipes as I have heard that the "donuts" go bad? or could the pipe itself be cracked? Any help would be greatly appreciated. Thanks

[Stroken7.3]

Check the pipe on the passanger side exhaust manifold, it is in the front. I think it is the exhaust back pressure tube.

[dieseldan2005]

x2 on that tube. It goes to the sensor right on top of the water pump.