I have a 13 2500 megacab and Im deleting this next week. Have some questions about exhaust.

I would like to keep the noise down a little so I was looking at the 4" without a muffler.

Is the stock exhaust 4"?

What is the benefit of doing the "turbo back" or "downpipe back" or "DPF back" exhausts in 4" if the stock is 4"?

When shopping for a new exhaust, I keep seeing "turbo back" and "downpipe back" and some other ones listed. What exactly am I looking for? If the stock exhaust is 4", I would prefer a much simpler install, so would a "race pipe" be all that is actually needed?

If the "race pipe" works and its really all I need, do I need to shop for one specific to a megacab or 2013 or is it all the same since Im just replacing what looks like the middle section of the exhaust?

Anything else I need to look out for when shopping?

Thanks folks.