Mine are quite a bit more than 1/8" and put a wrench on one of the nuts and it turned real easy. May be why I'm getting a lot more decel pop because of leakage.........Nip, you say yours are 1/8", but are they suppose to fit up flush?
If you just recently reassembled the header pipe and replaced the gasket with a new gasket, you may need to run the engine up to warm everything up, then after cool-down, retorque the nuts. You also want to make sure that when you installed the gasket, that you got it properly seated into the exhaust port and that it wasn't cocked. If the flange looks uneven, the collar on the pipe might be hanging up on the edge of the exh. port gasket recess.
A little more than a 1/8 inch gap may be ok, but it needs to be even.