Typically (from what I've heard) the bigger the exhaust the worse the low end torque but better high end HP.

So is it a good idea to install bigger exhaust for towing?

I'm thinking for me is a 4" exhaust would let the motor breathe a bit better and lower EGT's when I tow my 7K trailer over mountian passes here in the PNW..... But it won't be so large that it will drone or be stupid loud for long distance driving... Is my thinking correct? or would I just be better off keeping it stock.

Sorry - I'm such a noob when it comes to diesel stuff.....

 

I have had a 4" aftermarket exhaust on my truck for quite some time now. I also tow a 7500lbs. trailer and it really helps the truck breathe. As far as drone there is very little if any, my exits in the stock location.

 

I have a 4-1/2 inch exhaust. Pulling a 16,000 lbs. 5er. loaded. The extra size helps repel exhaust heat, back pressure from exhaust system, as well as help the turbo spool up faster.
My exhaust ends at the rear axle (with striaght through muffler) and I have very little droning in the cab. Oops, it might be my age and hearing in this late stage of the game.

 

Why not

get that mega mouth downpipe and a four inch exhaust? That will lower your egts a bit...

Rick