I have a magnex full decat, center with resonator and 6x4 b/b need to no how much louder will a afterburner b/b would be.

cheers daz

Erm, quite a lot.
I think :)

Also depends on how much of the system you change.
If you just fit the afterburner backbox and leave the resonated centre in it should be louder than the magnex back box.
Change the centre pipe to a straight through job and this will get alot louder. Choice is yours

WIll be just fitting the back box.