Title sort of states it.

I swapped an LQ4 out of a 2004 Silverado 2500HD into an older Land Cruiser. Aside from the exhaust manifolds, it is all stock.

I'm considering a different cam to gain some mpg and upper end rpm.

But currently, I am redoing the exhaust. I'm using C6 exhaust manifolds like:


The exhaust manifolds are going to be Jet coated.

Onto the question, will going dual help me with mpg and upper end rpms?

I was considering 2 1/4" to 2 1/2" dual. I am considering using a muffler like MagnaFlow 12468 muffler(2 in, 2 out)

One of the goals for replacing the exhaust is keeping the noise down a bit.

 

it wont hurt and its probably a better investment than shorties in you want LTs later on.

are going to have a set custom made?

 

I am having very bad luck with the Hooker Header shorties currently in the rig so I'm not really considering a set of headers.

From what I've heard of the manifolds above is they are one of the better fitting/flowing stock manifolds.

 

I'd go with dual 2.5" all the way to the muffler, then 3" all the way out. I'd make sure to use all mandrel bends. The single 3" muffler outlet will flow a little less than dual 2.5", but will quiet down the exhaust a lot better,
Go with the longest muffler body that you think will fit well to quiet it down the most.
I'd look at these mufflers that are all reversible.
Borla #40349, Dynomax Ultra Flo #17228, Magnaflow #12189 and #12288.

If you want no loss in flow(inlet to outlet) then go with a Magnaflow# 12587, and run 3.5" exhaust from the muffler all the way out, IF the case isn't to long at 22".

 

true dual exhaust is worth it on any v8 if nothing else just for the better sound