Header wrap?
 

Basic question, has anyone done their entire exhaust in header wrap? I’m guessing that keeping the heat inside the pipe would help the exhaust retain energy and maybe help the volumetric efficiency of the engine...

Yep, it will certainly help. How much? Dunno. :)

Unfortunately, wraps are well known to help your exhaust rot out a good amount faster.

Yea it helps. It also helps because it keeps heat out of the cabin. In wet states, on a daily driver, I definitely would not recommend you wrap your exhaust system(don't have to worry about this in Cali). As Doax pointed out, it will accelerate rust due to water getting trapped between the wrap and the exhaust. Now there are Silicone spray lube specifically designed for header wrap to combat this problem, but I have no idea how good it works in a long term scenario, especially on a car that gets driven on a daily basis.

I just considered doing some wrap on both of my Ions... at least the header/manifold and downpipe which would be better shielded from water by a belly pan... I also imagine that by keeping the heat inside the pipe I could cover at least my mid pipe with a coroplast belly pan without fear of melting(currently it’s open but my mid pan is trashed and could use replacing and solid would be easier to cut and install)

The header and downpipe on my Redline are heavy duty stainless so I imagine they’d take more heat related abuse...

I was also considering at least a better cast manifold (stock one from Redline/Cobalt SS)for my base model, and a better downpipe with bungs for wideband and EGT... wrapping was a consideration

Can't see how that would work. Cooling the exhaust reduces volume & pressure - basic physics, no?

And slows it down.

It also becomes more dense, and thus takes more power to push it out because there is more mass in the system.

The idea isn’t to cool the exhaust gas, but rather limit the radiant heat loss from the pipe, retaining more heat in the gas, improving velocity and torque...

Header wrap also likes to catch on fire when oil gets spilled or leaked on it.

That’s a good thought about oil spillage... I sometimes dribble a little when changing oil... maybe a ceramic coating could provide what I’m after...