New stock exhaust manifolds or headers?

[TollKeeper]

On the Yukon, you can loosen both sides and get plenty of slack in the headers by dropping them down with a jack under the y-pipe.

I, thankfully, didnt have to take off the passenger side. With the shoe horn job they did on getting that 5.3 in there, that passenger side is a bear to work on. I am thankful it was only the drivers side.

 

[Meccanoble]

I'm getting high flow cats installed hopefully this weekend and bought exhaust manifold gaskets and ARP bolts. I'm basically doing a header job without doing headers. I know cars with headers need a tune but weighing my options here. If I dont get a tune, will i suffer? Looking for reasons to not get some headers on amazon for cheap with good fitment reviews.

CONS:
Will most likely need new/advanced coil packs to fit around headers
Will most likely need heat wrap
Will most likely need a tune


PROS:
Better mpg
More power