What is the best muffler/ Exhaust system for a 5.9 Gasser? I want it to be louder, but not too loud. I was thinking of a full straight pipe, but I'm not sure if it would be too loud.

 

What do you have up front? Headers? Manifolds? Is the cat still there??

"Best" is really subjective..... there are a fair few videos on YouTube showcasing different exhaust set ups......

 

Straight pipe will be extremely loud and illegal. Get a catback. magnaflow, etc.

 

All stock, but i do plan on doing headers eventually.

 

Start with getting a stainless type, I got a Magnaflow, a bit louder though.

 

I decided to upgrade my exhaust system a few years ago to 3" single pipe from the converter on back. I'm using the following muffler and converter:
Dynomax UltraFlo Welded Muffler - 17233 (3" inlet and outlet) and Magnaflow Converter - 99047HM (dual 2" inlets, 3" outlet, front O2 sensor port). I had a muffler shop install my converter and muffler, since I needed a 3" straight pipe between the converter and the muffler (plus weld a bung on the straight pipe for the O2 sensor after the converter) along with a custom bent 3" tail pipe. As long as you're using shorty headers to replace the stock manifolds, this setup will work with either setup.

This system works well. The muffler flows well and the sound is pretty quiet until the motor revs to about 2500 rpm and above.

 

I decided to go with a flow master 40. Ill update on how it is when I get it

 

I installed the muffler, and so far i like it. It sounds louder, but not too much. I can still have a conversation at a normal level. It also feels like i have a little low end power. I would recommend for anyone who needs a new muffler.