i had EXACTLY the same problem. couldn't go over 2200 rpm's and hissed on the gas. to check the cat, i pulled the O2 sensor, and drilled a few holes in the pipe before it (you replace that piece with the cat anyway) sure enough, it ran alot better. IT IS THE CAT. mine also made the rattling sound too. get the magnaflow for like $150 from summit racing.
also, do it soon! i ran mine for weeks like that, damaged something that i'm still trying to figure out. i think its the front O2 sensor, which i will replace soon. you can also blow out your head gasket because of too much pressure, or burn a valve.

 

So is mine

 

BTW, yes what I explained earlier when mine sounded like it was choking was because of the cat


Here is an easy way to tell that you can do yourself. Crawl under and pull the O2 sensor BEFORE the cat out. That little hole will let enough gas/presure out for the engine to run at lower RPM. So if it works like that, its the cat, unless your muffler somehow ate itself lol

Also, take your VIN to the dealer (or call them) and see if your truck is part of the extended warrenty. If it is, you'll get a free cat [sm=partyparty.gif]

If they won't cover it, GET A HIGH FLOW CAT. They're CHEAPER and BETTER PERFORMANCE!

 

Well the results are in!! To all those who put your money on the fuel pump better fork it over to me because you were wrong. It was the cat. I gutted her out and now not only is the exhaust deeper and throatier but it has restored ALOT of power. I mst have been running clogged for awhile. But it never damaged anything. we checked her all out and everything was a.ok! thanks to everyone that helped with my problem and hopefully this thread will pass to someone with the same problem. Oh yes...NO MORE RATTLING!! [8D]

 

What year is your truck? If you have a downstream O2 sensor your gonna get a CE light with a cutted cat. You can get O2 simms though.

 

no CEL yet or maybe not at all....

 

Good job! Deffinately a lot easier and cheaper than a fuel pump. Nice to see someone get by the easier fix once in a while. Explains the exhaust leak/backpressure up front. The aftermarket cat system sounds like a good upgrade if you start to have EC troubles.

 

I have a 97 Ram 5.2 318, while driving to work it ran fine stopped at a stop sign went to take off and it fell on its face! It sounded like it sucked a intake manifold gasket. Took to stealer said Cat was bad. it cost me $400. Damn rip off Bastards!! Shortly later I got a rattling noise and the muffler was coming apart so I put a straight pipe in. Sounds so good.

 

I see by your slogan, I'm not the only one that eats up the left lane!!!!!! "Lead, follow, or get the he!! out of the way"

 

The speed limit on the highways in NY are 65. I CANNOT stand it when some bone head gets in the left lane and does 65 or 70. It drives me nuts!!! I don't know how many times I got the bird for riding bumpers!!! LOL..