In the latest Diesel Power mag is an ad for the turbo up pipes I referenced earlier $500 a pair (rifraff diesel). There is also a write up on the scan gauge and how it works. Aimed at the 6.0 but it also will work with 7.3 except it does not show boost or egt so you would need to add gauges for those functions.
A muffler by itself will help but a good exhaust will give the most bang for the buck. I run a Gibson, all mandrel bent tubing and free flow muffler, and NO drone in the cab even when pulling. We went last year with friends and the guy had a straight thru system and muffler and it will drive ya nuts. His wife rode with use for a bit and she was so happy to be in a quiet truck. BTW his is a dodge and they are noisy, particularly with the minimal mufflers many run.