its probably not the easiest answer, but if you pull the manifold youll be able to check the flange to see how warped it is, if its warped take it to a GOOOD machine shop and ask them to mill it just enough to flatten it out. make sure to cross torque your bolts just like you would wheel lug nuts, IMO thatll leave no way for the flange to warp again, also make sure to check the mating surface on the turbo it might not be the manifold at all