I would assume it would loose some noticable torque down low, but this is theoretical as a track day trial, i was thinking about trying it for a couple of runs. Last time i was there, there was a kid with a 99 Si I/H and running his exhaust straight off the headder (sounded like an 88 toyota with a rusted out muff) yet ran a consistent 14.8 all day long with no other mods. That is proof enough to at least try it and shoot for my high 13's