I have a 92 xlt. Before I bought the truck the previous owner had the system replaced from the manifold back, now the truck has a suction noise after you get off the throttle, when I checked it out there was a rubber hose coming of a port of the pipe on the tailgate side of the cat. The hose had melted off and thats where the suction was coming from, i put it back on and it was ok for about a week and it melted off again. I do not no what the port was for I'm guessing an O2 sensor but the hose was off when I got it inspected and it passed so I was thinking about capping it off, what do you think? Thank you.

 

Cap it off. That hose should be going to an air pump. Let us know how that worked out. If it goes to an air pump don't cap the rubber hose, as it will make the engine work harder to turn the pump. Let it just vent open.

 

Try running the truck and see if the air coming out of the hose is hot. If so trace it back to see where it comes from. Sometimes exhaust gases are used for other things. If something has stopped up and caused the ehxaust gas to be rerouted this may be why your hose is burning in two.

I had a Dodge van that the catalytic converter failed. It caused the plastic part of the EGR valve to burn up and cause the same sort of sucking sound.

Good luck.