I recently did the Hughe’s 1/4” Aluminum Plenum swap with my old plenum as it was very noticeably damaged and I was losing power when going up any kind of incline or trying to pull anything whatsoever. I also have changed the gaskets, and did everything by the book. I have a new radiator, all new brake lines, calipers, shoes and disks, rotors, master cylinder, booster, and fluid lines. I have new U-Joints and air filters and oil filter and oil too.

The Issue: I still notice an exhaust leak issue from where the catalytic converter splits and goes up and connects on the driver side connection where it enters the engine or valve cover area. It also gets super hot very quickly and I have not ran it more than 2-5 minutes when running it periodically to keep it somewhat in good working condition as far as allowing it to run without long periods of rest. I can tell a difference when I remove the 02 sensor in front of the catalytic converter housing or filter area (I don’t know the exact name of the area where it flares out and the honeycomb thing is), but when the sensor is removed it idles better. I believe my cat is clogged and can hear rattling when I hit with a hammer. Should I replace it? Can I run without it to drive to a mechanic 5 miles away?

It’s the area under the brake booster

 

I recently swapped out the plenum plate in the upper intake manifold area or that separates the upper and lower intake manifold I guess. I put in a 1/4” aluminum plate and replaced all gaskets trying to fix an issue I’ve been having where I’m losing all power when going on any incline and the valve cover area gets hot where the catalytic connector under the brake booster or master cylinder area is. And it is somewhat better when I remove the o2 sensor I front of the catalytic converter housing area on the exhaust pipe. But it’s only on the drive side connection and I think the catalytic converter is clogged or bad because if I tap it with a hammer it really rattles or something but what can I do to get to a mechanic or fix it myself? I have never had any check engine lights or any type of sensor lights come on this far but it’s an obvious issue and my valve cover gets hot almost immediately when I start it cold.

 

Merged duplicate threads and moved to the correct section.

 

Since the cat was bombed with oil from the intake plenum for who knows how long and given the age of these trucks, it is a good idea to replace the cat, since it's likely clogged. There should be no issues with driving it for a short distance to your mechanic for the cat replacement.