Enz512tr

Why are the outside pipes black while the inside two are perfectly clean?

onfire

Due to the valves inside. Only open a small percentage of the time and that percentage is a rich AFR mixture.

sTz

When in Sport or Track mod the NPP valves are open. Most of the exhaust flow is directed to the outer two tips. It's completely normal.

Enz512tr

Thanks for your reply. Also thanks to "OnFire". Got my 17 Z06 about a month ago and figured it had something to do with the valves. I've set the exhaust sound for Track all the time. Have also heard that I can remove fuse 42. If I do that, will the exhaust be evenly distributed through all four pipes or is it simply due to path of least resistance with most exhaust going through the outside pipes?

EMINENT 1

No. Mine is pulled. It does help the baffles stay open all the time instead of closing a bit when shifting.
Doesn't help distribute. Outer 2 are always dirty after a drive. Inner 2 clean for days n weeks.

I've decided to paint mine black this weekend. Sick of cleaning them.

sTz

As Element1 stated, pulling the fuse will have no affect on the soot. The outer two tips will still have more build-up.

Funny, I have the Corsa set-up, which deletes the NPP, and all 4 tips are equally dirty.

breakskeet

That is because the factory exhaust have 2 outlets per muffler and as you stated the pathway for the outside tip will make it gather more soot. The Corsa mufflers have only one outlet so the tips which "Y" off the single outlet gather the same amount of exhaust flow and therefore the same amount of soot.