HorseHauler

explain that to the fella that cracked his exhaust manifold and blew his head gasket because of a plugged cat... sorry I forget his name...

Lark

When he told me that, I don't think he was referring to the performance aspects of a plug'd cat.

HorseHauler

I know, I'm just saying with long term use, the cat will decrease it's effectiveness of flow. I agree that the muffler is the biggest restriction.

Lark

Diesel Performance Shop told me 80% of the restriction (new Cummins motors) comes from the stock muffler and the rest from the cat. He said, however, you reverse those numbers for noise. From my own experience, I would have to agree with him.

Tree DR

So what is the answer then????? Put a straight through muffler in place of the cat and deleat the stock muffler????? That should eliminate most of the noise?????

Lark

I believe the answer that is right for "you" is either put on the BIG Donaldson in place of the cat AND muffler, or put back on a cat and get a 30" Magnaflow if you're not wanting a lot of noise.

I can't guarantee the results from the first option, but I KNOW the second option works. Good luck.