Yes I am running into problems that is why I am using the 3.5" Down Pipe's.
I understand about the diesel trucks I have had a few and have a Diesel Excursion right now.
I will be stepping it up then for sure and will need to resource some parts to try and make it a 5" exhaust with and X Pipe to mufflers dumped at the axle..................we will see.
I have a few other ideas about running the exhaust just behind the Front Tires on both sides without even using any mufflers at all. So it would be a very short route to the atmosphere like that! Less back pressure for sure.