Not sure.
The chamber mufflers pulse I think is what hurts the turbos final power.

 

Ive got the magnaflow 30" diesel with a resonator tube and its still loud. I havent found a way around loud and 4" exhaust.

I may add a cutout after the DP and reduce the muffler to a 3" large case magnaflow.

Stock48 made well over 700 rwhp and 10s on full 3" exhaust years ago which is far more than i could claim.

The thing that gets us with extender cabs is the length of piping. Even with full 4" im still probably pushing 10-12 feet of pipe out the rear end.

 

Anybody run one of these? Its 30" body, 4" in/out with a 3.5" core. MagnaFlow Exhaust Products - For Trucks, Suv's, American Muscle, Diesel, & Sport Compact Vehicles

 

What about stacking to mufflers. Along time ago when i was NA i put 2 mufflers in series. One round and one oval. I think i could fit 1 round and 1 oval like i did before. My 3.5 magnaflow muffler is really quiet but the case on it is HuGe.

Something like this but in 4in is what i am thinking.

 

Diesel muffler will be your best bet but their size will scare you off.

I got a 5in muffler on my truck and it was too quiet but after couple of 23 psi pulls it got louder.

Here is a short video clip hitting on it but you get the idea.

Skip the first 40 sec dyno.

https://www.youtube.com/watch?v=caagn9ym3ks

 

when my exhaust iwas to loud I was able to add resonators to tone them down worked out well a few time for me

 

I agree with the diesel muffler. I had a 4" Donaldson diesel muffler and it was super quiet. All I heard was my turbo spooling up, however it was 40" long and 8" diameter.

The SIZE will scare you.

I swaped to a corsa diesel muffler for more sound and turbine whistle.

 

So a corsa like this?

http://www.summitracing.com/parts/cse-8004000/overview/

 

Yep I had Donaldson and the price wasn't bad. We had to shorten the muffler to fit.

 

Here is what I was thinking for my setup. This muffler with 4" to dual 3" exiting on the side in front of the rear tire. Not sure if the Y in the muffler would hurt airflow but it's probably quieter than a 4" straight thru.

MagnaFlow Exhaust Products - For Trucks, Suv's, American Muscle, Diesel, & Sport Compact Vehicles