this is prob a stupid Q but do stacks lower your egts? less pipe it has to go though.

 

no at least not enough to notice

 

I noticed a difference when I went from two 5 inch stacks to one 7 inch stack. IMO other than a hood stack a single stack is the best exhaust system performance wise

 

Stacks will raise egts. I noticed about a 75-100deg rise in my dual 5'in mitres vs the 4'in straight pipe. My best guess for the increase was because with the stacks I was adding/creating back pressure, where with the straight pipe there was no back pressure

 

that would be due to all the extra pipe and bends

 

which is also why you saw a lower temp with one stack; you took two 90's out of the equation... i'm sure the 4" straight pipe didnt have a true 90 bend until the outlet; so... depending on how restrictive your exhuast is right now you may or may not see a drop in EGT's

 

another reason i want stacks is so the soot stops gettin all over the side on my truck. i love 2 roal coal just dont like it all over the side of my truck

 

Now you'll have soot all over your tailgate...

 

and all over your roof when it rains and on stuff you haul in your bed, if it is parked outside and you dont like soot then you better get a rain cap aka 'flapper' or your whole truck will be covered in soot...trust me

 

yeah unless you really stick those stacks up like 10 feet over your roof on your pickup you're gonna get soot all over the tailgate, turn down tip is probably the best way to calm down smoke getting on the pickup but not the best looking imo