whats the average torque loss when you go from having a full exhaust to open header?

 

I would say zero

 

I don't know how much it lost. I had the SLP LM and went to a Borla muffler directly off the Y-Pipe w/ small turndown. Lost alittle on 60 ft and about .75 mph average on 2 diff. trips to the track. Sold the SLP LM and this is all just a temp setup.
Now on the nitrous, it's a different story. I went from 7.8x=7.9 on motor and 7.08-7.2x on spray!! Makes me want to get a cutout when i install my TSP headers and TD's.