With fear of sounding like an idiot, I actually looked under my truck tonight and actually looked at my exhaust since I am considering an MBRP kit and there is no cat. Is that a normal thing in the early years of the Duramax?

Yes that is normal. Not all states required a Cat in 2003.

consider yourself fortunate that you don't have one. You could just delete the muffler on your truck and it would sound awesome! Poor man's straight pipe.

WOW. I am in Pa and I bought the truck used in the Pittsburgh area a couple of years ago. I don't want to mess with the sound too much or have any drone in the truck when cruising or towing so I am hesitant to change anything.

My 02 has always been a PA truck and it did not come with a cat either. I may be selling my Flowmaster system if you're interested... It's still on the truck so depending where you are we could connect and you could hear it.

Mine didn't come with one either...:)

only the LLY trucks and on, and the California duramaxes have cats that i know of.

My 02 has always been a PA truck and it did not come with a cat either. I may be selling my Flowmaster system if you're interested... It's still on the truck so depending where you are we could connect and you could hear it.

Thanks for the offer. I am in the Reading area but I work in Philadelphia if that's any help. It would be interesting to hear. My truck is an extended cab short bed so it might not work anyway.

My 03 came with a cat, I got rid of it, straight piped it like stated above, and it saved me 3-400 bucks on a exhaust.

The sound is not loud, unless I really get on it, and it will accomodate up to 450HP or so, so like many folks I asked about the exhaust, they got rid of their straight pipe for the 4-5" system, and said they noticed NO difference with thier application, and wished they saved the money and stayed with the straight pipe.

Just my 2 cent worth.

Maybe I will give that a shot since it won't cost anything and I can always spend the money later. Did you notice any power gains removing the muffler?

No power gain, and I asked many people who had the straight pipe who then went to the other aftermarket systems, and they said there is NO difference, and to save the money.

Now if you were looking into making over 450HP, I would then be looking into a bigger aftermarket system, but then if I were to be looking to make more HP, I would throw money at it to get there.

it just depends on the quality of the exhaust. if you have smooth bends, you will definately notice a performance gain. the straighter the flow with less resistance will give you a gain. first, i just straight piped my factory exhaust at stock power level. added a tuner (PPE HOT +2) and kept the stock straight exhaust for a while. felt somewhat sluggish. i ordered several 4" mandrel bent 90s, and a few 4ft sticks of 4" pipe then made my own exhaust. there was a tremendous gain, it also sounds way better than did the stock 3.5" pipe, not to mention a 250 degree drop in egts. if you have no power adder, the stock straight piped exhaust is good, but i would recommend a good 4" with any tuner or box.

I have a TST tuner and I tow with it so I don't really want a bunch of noise at WOT.

So my '05 LLY should have a cat? I bought it used without. Planning on a Turbo back MBRP in the near future.

all the LLY trucks i have modified had a cat. as long as you are not throwing codes you are ok. the lb7s sound good with the mbrp exhaust. not too loud, but a good deep tone. if you go without the muffler, it will be pretty loud. mine had a lot of ressonance in the cab with the 4" straight pipe and dual 3" outlets towing until i made a resonator.

Some California Lb7's Came With Out A Cat As Well. I Have A Buddy With One Here And His Didn't Have One.

Some California Lb7's Came With Out A Cat As Well. I Have A Buddy With One Here And His Didn't Have One.

He probably had a 2001 LB7, I think 2002 was the 1st year in Calif. with a Cat unless it came from out of state.

Thanks for the offer. I am in the Reading area but I work in Philadelphia if that's any help. It would be interesting to hear. My truck is an extended cab short bed so it might not work anyway.

mrhockey, I'm a bit south of you, between Carlisle and Chambersburg, 10 minutes off I-76 and/or I-81. Let me know if you get down this way.

mrhockey, I'm a bit south of you, between Carlisle and Chambersburg, 10 minutes off I-76 and/or I-81. Let me know if you get down this way.

Yep I know where are at. I don't see myself getting down there anytime in the future but thanks for the offer.