I am convinced my cats are plugged up and I could use some help. I posted about this last week in the supercharger section, basically I supercharged my truck and I think the air/fuel ratio was off and it melted my cats. I am getting about stock horespower with a supercharger according to my dyno last week. Aside from that I have a 6" lift and so does my friend on his 5.3 chevy and we both have 35" tires, his truck is faster than mine with stock gears, exhaust, and no engine modifications. I know something is not right. My supercharger is supposed to make 7-8psi and I am getting 10-11 which the tuner thinks is from back pressure from a clogged cat. I also have next to no acceleration on the highway at wide open throttle, which I've read is an indication that the exhaust isn't flowing out like it should.

I dont know what to do at this point. I visited 4 muffler shops today trying to figure this out and I'm still stuck without an answer. 2 shops wanted me to replace the cats which I was quoted over $800 for the left and $600 for the right cats alone plus labor. I had someone willing to gut them out for me until he got under my truck and saw there are 4 cats on my truck and he said it would be a lot more invovled than he wants to get into with the pre cats being tucked way up like they are.

Please give me advice what to do. I am going to try to pull the 02 sensors out in the next day to see if I get more power because exhaust can escape from that hole to help me verify it is clogged cat. Is it possible that the cats blew out and the remains are stuck in the muffler? I'm at a loss right now and I don't want to spend $1,500 to fix my cats. If there is a good way to delete the cats for now until I can get high flow cats and an X pipe or a cheap setup like that which I could do please let me know.

My truck is a 2004 5.4 3 valve currently I have a dual exhaust on it from the muffler back.

 

Buy a pair of 94016 high-flow cats and cut out the stock 4. You can get them for $96 on performance peddler with the "clubgp" code. Then find a shop that doesn't charge your soul for that kind of work.

 

test the backpressure on each set of cats with a magnahelic gauge via the o2 sensor bungs after the cats

 

Yes it is possible for a cat to blow out and clog the muffler.

Instead of taking out the o2's you can just loosen the exhaust pipe where it bolts to the manifold, but only for a test run. It will throw a code though and if you continue to run it open you can do motor damage or even have a fire. THIS IS ONLY A TEST.

Also check this link. http://www.aa1car.com/library/converter.htm