Clogged Cat??

[Hotwheelbill]

So,
A co=worker told me that I may have a clogged Catalytic converter as he could hear a blockage when I tapped the throttle. I got out and let him in my trruck and I could hear it too. Like a little bog down sound at first when you tap the throttle.
I also had a very touchy throttle and hesitation both at start and going down the road. I can be going 70 or 30 and feel a type of serge going on. Hard for me to explain, but just not smooth!
I changed the TPS and it fixed the throttle jerk. Yesterday, I had cat back duals put on and , again, it helped the start from stop lag, but I still have a serge feel at all speeds. Last night I did a fuel psi test. Running was 54 psi. When I turned it off, it was 55 psi????? Held 55 psi for 7 mins and then down to 45 psi after 15 mins. What does that tell me?
I took a laser therm. to the exhaust and with engine hot and at idle, both cats where 500+-. Before and after were about 300+-. Manifolds were even temps frrom front to rear.
Any help please.
204k miles on what I am sure is stock cats.

 

[michael hurd]

The outlet of the cat should be hotter than the inlet by 100 degrees or so. Sounds to me they may be partially plugged. The fuel pressure seems low, especially if you still have the poppet type injectors.

 

[Hotwheelbill]

Yeah, I took it back to the muffler shop and let him drive it. He said same thing.
SOoo, hiflow cats part numbers please??

 

[Hotwheelbill]

Just an update.
It was the Cats backing up the motor. New high flow cats and what a difference!!!!!