I am thinking of having the muffler shop remove my stock muff and replace it with straight pipe. Has anyone done this? Will I lose/gain low-end torque? Will I lose/gain horsepower? Or will I notice no change except that it will be louder?

I can't seem to find any info (other than opinions) about the effect backpressure has on torque. I have found alot of credible info that reducing the backpressure will increase H.P., but it is torque that I am more concerned about. I want to keep or gain torque, not lose torque. H.P. is not as important to me as low-end torque. Loudness is not an issue either, as long as it doesn't sound obnoxious.

Please post any links to dyno tests or sites which have credible data on the effect of exhaust mods to torque as well as horsepower.
Thanks guys.