Well, do you have your res still??? I am running stock headers and precats, off road y, and a res. You can see what it did for my dyno in my sig.
As far as backpressure. I could not really tell you. I have heard reasons for both sides. I see less back pressure more hp, more TQ. I am going to eliminate the pre cats in the near future. Are you running MIL's?
Merlin
281hp 324tq
Timing 14' FP 36,24lbs,190lph,75Maf,65tb,cobra upper&lower,B303, GT-40 Crate with X al heads, Mac shorties, Off Road H,2chamber Flow's dumped, Tokico 5wys, Hotichkis Ctrl Arms, Alum Drive shaft, 3.73, Sub Frame,Steeda Tri-Ax, 94 Seats Drivers side powered.
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