Would you gain/lose HP if you just ran straight piping from the headers till the end, and maybe a possible h/x pipe. No mufflers or anything like that.
Yes and no. If you had just two straight pipes, one for each bank, then yes you would lose hp; however, this is over a exhaust system with a H or X pipe. A H pipe and X pipe baffels (balance) the exhuast out, which gives you better exhuast flow. A X pipe baffels better then a H pipe, but a H pipe usally gives a deeper sound. Now, the mufler will always cause a hp lose, but might cause a torque gain. In the end though, I would say run mufflers. Not only is the power gain not that much, but (and this will happen no matter what you think) the noise level will get to you. Trust me, I ran my car with open headers for 3 weeks.