I have a buddy of a buddy whom told him that he would install a flowmaster 4" after cat system for $450...I was planning on buying and mbrp system but this sounds like suck a good deal... I figure he is using his own piping and only using a flowmaster muffler... now my questions are these...
1. does flowmaster make a diesel muffler and if not are mufflers universal between gas and diesel?

2. anyone ever done this themselves and what were there thoughts...

Thanks so much gentlemen!

mjlater,
I had a Flowmaster Series 50 Model 53553 muffler installed on my stock pipe system (3 1/2") in January. Cost = $252.37 installed.
Last week was the first time I have pulled my trailer in the MO Ozarks this year and I can tell you that the muffler alone lowered my egt's from approx 1380 to 1200 max. Most of the time my egt's stayed around 1050 to 1100. For comparisons with OEM muffler outside temps were approx 90 degrees F and the outside temps with Flowmaster were the same 90-92. 5er wt = approx 10,300 lb.
I was told by local muffler shop the 53553 is for the '03 LB7, but looking at Flowmaster info I can see it is not just for that truck and it appears it is not limited to just diesel.
With this conversion I also picked up the dreaded 1600-1900 rpm drone, but that is irritating to some and loved by others. What can I say?!

mjlater,
I had a Flowmaster Series 50 Model 53553 muffler installed on my stock pipe system (3 1/2") in January. Cost = $252.37 installed.
Last week was the first time I have pulled my trailer in the MO Ozarks this year and I can tell you that the muffler alone lowered my egt's from approx 1380 to 1200 max. Most of the time my egt's stayed around 1050 to 1100. For comparisons with OEM muffler outside temps were approx 90 degrees F and the outside temps with Flowmaster were the same 90-92. 5er wt = approx 10,300 lb.
I was told by local muffler shop the 53553 is for the '03 LB7, but looking at Flowmaster info I can see it is not just for that truck and it appears it is not limited to just diesel.
With this conversion I also picked up the dreaded 1600-1900 rpm drone, but that is irritating to some and loved by others. What can I say?!

You did exactly what I've been thinking about doing but since you've picked up that drone, I'll just stay stock on the exhaust. I had a REALLY BAD experience with a 1/2 ton Dodge gasser I had with a Gibson cat-back. Had to take it back off & go back to factory, highway racket drove me crazy!-:t

When towing the "drone" is naturally louder and I am thinking I will go with tts 4" exhaust to relieve this. Most of my driving is non-tow, at 70-74mph on I-55 turning 2200-2300 rpm so the drone has been "manageable". Some of the younger group would think it's not loud enough, but to me after about 75miles of having to shout to someone in the passenger seat while towing is too much effort.