Exhaust Manifold Question?

[RallyStarion]

Can anyone tell me if there is any difference in exhaust manifold design thru the models. The manifold on my engine appears to be a split pulse set up ie. 1 & 4 pulses are seperated from 2 & 3 as they enter the turbo. The manifold flange is distorting with heat ( probably the antilag ) and I am reluctant to machine it again. What is a standard set? Has anyone had one made?
Thanks.
Brian.