Header Gasket Troubles..

sometimes the less expensive headers will reduce mfg. costs by using thinner header flanges, which can become problematic to seal. One trick you can try, is to weld a short piece of 5/16" or 3/8" key stock along the top side of the (middle two)header tubes/ outside of flange to make it more rigid and less-prone to "banana" the flange surface when you tighten the bolts.