Some people may argue differently, but a 4in exhaust is a 4in exhaust 'dunno; The sound isn't going to be much different from each other when comparing straight to straight basically.

But yes, MBRP is a good quality exhaust from my experience. I've installed a couple sets myself and they're not bad.

I've got a set of Diamond Eye 4in duals on my LB7 and I won't lie-good exhaust, royal pain to install... GrrRRrr

My last two exhausts I have put on my own trucks have been MagnaFlow 5in. By far the easiest installing and best fitting out of the box I have ever installed.

 

What is the big difference between the 4" and 5" besides the size.

 

Literally just the amount of air that flows through it, might make it louder with a 5” also. No real performance gain between a 4” and 5”, just personal preference really.
Although some do say 4” for performance and 5” for sound.

 

I'd buy Flo-Pro if I were to redo mine. Mine is mbrp, and I do not like that they are sleeve fit rather than clamp unions. can be a bit of a pain in the ass to separate them if/when you go to add a muffler/resonator

you'll get more exhaust noise than you bargain for with a straight pipe on a LB7. personally I would run a 30" FTE resonator where the muffler would normally go to knock the drone down, which will be significant on a LB7, but not make it much/any quieter

 

I put a 4" MBRP on my 04 didn't fit that great, drones when towing. Sounds fine when no towing though.

 

I run the 4 inch. Good fit,has a good sound

02 gmc sierra 2500hd crew cab short bed
3" zone kit
285/70/17 nitto Terra Grapplers
17x9 Raceline 930's
S&B intake
3" turbo horn
PPE boost valve
MBRP 3" downpipe
MBRP 4" exhaust
boost auto tow mirrors (dual function) Edge CTS2 with EAS EGT probe
LED conversion
Fass 90

 

I wont say that i was wowed by the MBRP kit i got, the instructions were lousy and did not match the parts i received.... however, it does all fit, work, and is nice and rigid once installed so i really cant complain, especially at the price point its at. I opted for a muffler on mine and dont seem to get nearly as much drone on the highway as others have commented on from a straight pipe.

What is the big difference between the 4" and 5" besides the size.

Unless your producing tons of power where you have the exhaust flow to utilize the larger pipe, there is no difference besides maybe the tone. the 5" is more likely to drone on the highway also.

 

the mufflers that come in the kits are trash, may as well throw those in the scrap bin. I'd spend the money on either a FTE resonator or a MBRP "quiet tone" muffler. I have both a 12" FTE resonator and then the quiet tone muffler and I'm thrilled with the result after being straight piped for 5+ years. you tell yourself it doesn't drone in the cab, but holy hell the difference you notice when it's not there anymore. my LBZ still has a nice low idle and it's definitely not much quieter than the straight pipe was at idle, but off idle and under acceleration it is somewhere between stock and straight piped, with zero drone in the cab.

if you want more volume, run just a resonator, won't cut the sound down by much but the lack of drone is worth every nickel

 

the mufflers that come in the kits are trash, may as well throw those in the scrap bin. I'd spend the money on either a FTE resonator or a MBRP "quiet tone" muffler. I have both a 12" FTE resonator and then the quiet tone muffler and I'm thrilled with the result after being straight piped for 5+ years. you tell yourself it doesn't drone in the cab, but holy hell the difference you notice when it's not there anymore. my LBZ still has a nice low idle and it's definitely not much quieter than the straight pipe was at idle, but off idle and under acceleration it is somewhere between stock and straight piped, with zero drone in the cab.

if you want more volume, run just a resonator, won't cut the sound down by much but the lack of drone is worth every nickel

https://www.youtube.com/watch?v=C4dUJl71P3A

yea thats what i have, the quiet tone muffler. Keeps the truck reasonably quiet up to about half to 3/4 throttle which keeps me from pissing off all my neighbors when the trucks warming up in the morning and driving out of the sub division. I plan to add the resonator at some point as well, just haven't gotten around to it.

 

I have heard good things about Flo~Pro Twister Resonators

I have heard quite a few good things about the fitment, size and sound quality from the Flo~Pro Twister Resonators. Come in different lengths or diameters for 4" and 5" pipe. Best location to install is underneath the cab. $71-105 depending on size. Get (2) LJ400 4" clamps ($12/each) or LJ500 5" clamps ($13/each) and you are good to go :smile2:
https://dalessuperstore.com/search.html?q=twister&go=Go

 

I was so concerned about noise and drone on my 06 LBZ so I bought the cheapest thing I could find and threw it on just to try. It has a resonator up front and a muffler in the back and I absolutely love it. Has a little rumble and absolutely no drone...

DIAMOND EYE 4" EXHAUST 01-07 CHEVY GM DURAMAX 6.6L DIESEL QUIET TONE TURBO BACK

I think it is the same low grade stuff (crap?), just a different name. Next to the tune. this is the best mod I have done to my truck so far.

 

I put that same diamond eye exhaust on my 03 last year and I love it. I used to run stock exhaust straight piped, and it just got to be too obnoxious.There is zero drone and it sounds so much better. It is much quieter but it has more of a low end rumble instead screaming 24/7.

The clamps that came with diamond eye are starting to rust, so if OP gets them, I’d use different clamps.

 

A buddy at work has a 4 Inch straight an I have a 5in straight , outside of the truck there’s no difference, inside the truck mine drones at most speeds his has a hint of it. If you plan on leveling your truck with drop shackles I’d say go with a 4 cause my 5 beats off the axle, actually it lays on it haha we car pull for work every other week an have been for over a year, we’ve heard both trucks at all rpm’s an speeds an in our opinion the drone is the only difference

 

I Have a MBRP 5" myself havnt noticed anything except its a tad louder than the 4" straight pipe I had on. Mine went on fine I put it all on one day about an hour to install, used the factory mounts as well. Next day I marked everything and welded it all together, I dont care for clamps. Your not going to get any noticeable improvement in proformance really unless you change The Down pipe and put on better manifolds. Biggest bang if your going to do that is a Bigger Turbo as well since its easier to do it all at one time. Oh and good luck not breaking any bolts!

 

Junk wont sell downpipe back for trucks with emissions to the USA. Scared ass company. They sell dpf filter back . Why the hell would I want to keep that garbage flow limiting dpf filter on