i would say that short headers are more probable to make less torque at low rpm due to the shorter primary tubes.the basic on how you build full lenght headers is that the longer tubes makes more torgue while shorter tend to give more power at the top. as for the hedman shortyheaders im not fully impressed by the design,the pics i have seen have seemed liked they dump in a stupid spot and in a stupid dirrection.
you could always repair your present headers by cutting out the bad sections and welding in new sections made with universal U or J bends. im sure your local dealer will sell you plenty of hooker part#12536 #12540 #12542 these are J bends made of 1 5/8" tubing with a 2" 2½" and 4" radius for about 250sek each
