Just what the title says, what sort of gains can you expect from a shorty header, such as the Cobalt Addiction V2 versus the gains from say...the ZZP midlength. We're assuming they're both bolted up to a DP. This is based on shorty vs midlength or even long tube to show the exaggerated effects of it. Which one will you gain more up top HP vs gain more low end torque.

 

Both will gain the same amount of peak HP.

The rest of the powerband is what the length effects.

Long=low, mid and high

Mid=mid and high

Shorty=high

 

Shorty vs. Longtube has been in debate for a long time. Shorty gives you high end, long tube, more low.
It's all about where you want your power. How do you drive your car? Hi- or Lo- end? Daily driven or track regular? Slightly modded car? Or smaller pulley, custom tune, and cat-back exhaust?
You have to match your system, also think about future mods...
For all intents and proposes the zzp midlength header and downpipe combo has always been a hit.
Cobalt Addiction also has a good setup.
JBP is a longtube design, but sounds like sex.
Or you could go GMPP and stay safe with warranty...
What sort of "seat of your pants feel" really looking for?

 

my plans, as they stand right now, involve a 3" or 2.9" pulley, CAI, aftermarket H/E, and the exaust is up for debate right now. My worries involve the fact that even though decent HP numbers are pulled from that setup, the torque gains are much smaller. I would love to get some good AutoX use out of this and have it to really be able to pull out of turns well without downshifting like hell to get through them. I may be willing to sacrifice a bit up top to get some more grunt.

 

Yes you will see gains in HP more than Torque. That is the nature of the beast, with the M62 that is...
Like I said before, the long tube is good for the "grunt" you speak of, and I would do the rest of the mods you have in mind, and then tune for it...that is really the key.
Once you have all your parts on your car, tune your car for that.
That is the best thing that I ever did, spend a day at at a dyno, let them pull 8-10 times on the dyno and figure it out...bolt-ons are insignificant compared to a tune...