power gain from hedder install

[SC2000GT]

I have a 2000 gt with the following mods:
vortech sq trim w/steeda tune
steeda boost pipe 10psi
bbk off road x pipew/stock exhaust manifolds and stock cat back
fms 70mm tb
trick flow upper plenum
3.73 gears
The car dynoed at 386HP and 369TQ before the upper plenum through the stock cat back.the car has ran a best of 12.39@113mph with the cat back unbolted.My question is if i install bbk long tubes how much hp will i gain and how much faster will the car go at the track? Are the hedders worth the money and install hassle?

 

[reeber]

I have a very close setup to yours... I am installing headers soon.. I am just real close to what my short block can handle, but in previous applications, it gave me 11 HP with a good tune and about .3 in the quarter mile..

 

[back_in_black]

from what I understand the lt's will drop your boost a little bit, which is good, less back pressure and also take the unwanted heat away from your engine faster as well, you can't go wrong.