I just purchased a 2003 3500 SO and it doesnt have a cat ..My question is did they come with one.... and what is the best muffler change out for power and fuel milage..

 

The 2003-early 04 did not come with a cat, they had a resonator. The 04.5 had a cat, and every year up had one.

The best muffler for power and fuel mileage is no muffler, but Donaldson and Hushpower are a couple of the big names out there now for straight through mufflers.

 

aeroturbine is a good one too.

 

I could be wrong but way back when I bought mine I was told depending on were and when the truck was build decided on if it came with a cat or not,mine did not,when I get asked about it I tell them and the plate proves it it was build in Mex and that time frame they did not place them on,I removed the muffler and so far I do not have any issiues with inspection or anything,some places of course would say something about it but I belive there are muffler look alikes you can get to make it look good.

Pav

 

03-04 California trucks got a cat, I believe, 235HP models.

 

My 03 low hp came with a CAT and muff. Some models did and some did not. I got lucky I guess. When the CAT left I picked up 3-4 mpg! Never had a problem with the law.