I started hearing what sounded like a small amount of air seeping out somewhere passenger side, under the hood. I could not place the noise which occurred for a few days. I then made the trip from Denver to Vail and the noise got increasingly louder. By the time I made it to Vail, about a 2 hour drive, the noise sounds like a Harley or something. The truck sat for a week or so and when I started to drive, the check engine light was on and then started flashing. I immediately put the truck back in the garage and turned it off. What does this mean? I could not find any holes or cracks in the manifold or in the cat. I pulled the following codes: P0304, P1314 and P1316.

 

Flange gasket can see if you do Sea foam treatment, will show smoke

 

The down pipe under the flange is also bad about separating.

 

Sorry, but what flange?

 

also, is it ok to drive it like this?

 

The triangle shaped flange that connects to the y-pipe. I have had to weld the down pipe back to the flange.

 

Hot exhaust leaks tend to melt stuff.

 

Buy a bottle of fuel injector cleaner, just get the cheap bottle because you are going to waste it.
Start the engine, find a small vacuum line and stick it into the bottle of fuel injector cleaner.
Look for the smoke.
You have then found your exhaust leak.
Let the engine idle until the smoke is gone.
You can drive it to the muffle shop, but keep it within 5 miles or so if you can.

 

See pix.
See black smudge where hot exhaust leaks out. Gasket inside is gone. Can feel when engine cold and started up. Induction cleaning made smoke pour from it.
See bolt that is now one with the rest of the surrounding metal.
See me wait on this little project....

 

Thank you everyone for your input, but I did not realize that I also have a pretty severe lack of power. Where I live, the speed limit is only 25, so I did not realize the lack of power at first. Could this be blocked cats?