im gettin stainless works headers on my trailblazer ss. Im just wondering for those guys that got long tube headers on their trucks how much louder does the truck get?

 

Long tubes kind of "ring" a bit. It's hard to describe but at first it will sound like there is an exhaust leak, but it's not a putt-putt leak, you'll just hear the exhaust ticks through the tubing somewhat. Then there is the tone of the exhaust itself...
Long tube headers come a lot closer to being balanced than shorties or a stock manifold can. The result is even sounding exhaust pulses with a very deep background rumble. Even keeping all other things the same, longtube will sound awesome on the LS2.
I've had the stock manifolds, shorties, mid-length, and now balanced equal-length long tubes on the Tahoe. The long tubes sound great - no contest.
Edit:
You asked too about louder. Underhood noise will increase. If you are used to stock sound levels you might consider the increase significant. It's not annoying and it will sound mean at idle, definately expect an increase in noise.

 

I changed to Magnaflow muffler too but mine is a little louder and has a good throaty sound to it. It's perfect.

 

Mine got slightly louder, but mostly more underhood noise. Barely any change at the tailpipes(s), until I removed them...now it sounds awesome IMO

 

it will make it sound better all around IMO.. a little ring like was said before but its not bad sounding. if you end up running cats the sound will most likely be just about the same as before.