heys I've checked with a certain performance shop mechanics, he said if whatever manifold you getting is good quality, it'll fit exactly...
however chances are your manifold will be made in China, there'll be a bit off missmatch, you just have to bore a wider hole for some........
also as you purchase the manifold you have to make sure 3 things
1- all surfaces are flat, the flange where the manifold connects to the engine block and the connection to the turbo (sit the surface on the ground to check, machine them if they are slightly curved)
2-The manifold lengths have to be relatively simmilar, if you have two longer outer pipes and a much shorter inner pipes it will cause some heating and backpressure problem in the inner manifold
3- where the external wastegate pipe is welded on, make sure the position is where all the 6 pipes joined. Some manifolds have their external wastegate inlet welded onto one pipe only. Not a good idea as the pressure from the remaining 5 manifolds will not be released, causing overboosting problem
and performance wise, it is not recomended to change unless necessary such as changing into top mount turbo
cheers