cApTaInGoOfY

Just got me a 1999 F150 Scab 5.4L Auto, it didn't have a muffler or tailpipe on it so I installed a Flowmaster 40 and a new tailpipe. But after the install, I can hear a leak when its cold but when it warms up it goes away. Sounds like it is coming from the passenger side where the exhaust manifold bolts up to the Y tube. Is there a gasket of some sort that goes there? I put my hand right there and I can feel air around this area. But again when it warms up, it is quiet.

TLB4

The piece that goes in between is called a donut. You can probably look it up on google images by searching exhaust donut. Basically it's just a compression fitting, but they do rust out.