Ford F-150 Runs rough and loud when cold

I have a 1997 Ford F150 with the 4.6L V8 and 170,000 miles on the odometer. Recently the truck started running oddly. When the engine is cold or has been shut off for a few minutes, a loud noise can be heard coming from the driver side of the engine. It sounds like there is a hole in the exhaust system under the hood. In addition, the smell of mixture rich exhaust gases comes into the cab and can be smelled under the hood. After a few minutes, the sound goes away, and the engine sounds and runs completely normal. Until the sound goes away, it sounds like I'm running open pipes when I'm accelerating even just a little. I checked the EGR valve and EGR vacuum regulator. I checked for voltage at the DFPE sensor (though I did not check the sensor itself). I checked for cracks or leaks in the EGR pipe. I also checked for trouble codes. Everything seems to be okay. The only indication I have from the OBD was a check engine light yesterday (1st time in 2 weeks). The trouble code indicated a misfire for cylinder #2. I replaced the spark plug wires as well as replaced and gapped the spark plugs over the summer. Any ideas?