paper gasket with orings and a heat sheild sounds like a stock manifold gasket. If you use this on a header the only problems would be a fitment issue with the ehat sheild, but it can easily be bent. The copper gaskets that i have seen, like the one from LC Engineering do not have holes for air injection, so if you still run air, then that gasket wont work. I agree on keeping proper bolt torque. I use a star washer under the nut in an attempt to keep the proper torque. Also, if you do use some type of silicone, this is one of those occasions where more isn't better. Just a thin layer. Too much and gobs will smudge out and go down the exhaust, where they could damage the O2 sensor or the catalyst. See if they have a high temp "sensor safe" type. what type of header is it? If it is they type with "welded orings" on the flange to header surface (like a thorley), then make sure you put something behind the centerof the header, as this area isn't the same height as the rest of the header. I used a washer on all the three center studs then put the header on to take up space. With out this you run the risk of overtorqueing the center nuts and making the ends of the header pull away warping the flange. I fought that for a while before i figured that out.
