If you have an oxygen sensor whatever you do make sure the system is air tight. After the sensor down the line I didn't even use gaskets and all my welds on my system have pinhole leaks, but it doesn't matter, downstream of the sensor. My manifolds had cone shaped stamped steel donuts and used a flared end on the pipe side that was clamped on with a 2 hole flange. I just copied the stock setup by getting 2 pieces of pipe flared at a nearby custom exhaust place, then cut off the flared end to use on my setup. The cone gasket is nice makes a great seal but without it I would recommend the three hole flange or a ball and cup socket to make it solid and leakproof.