im in the process of finishing my b18 swap in a eg sedan. the motor came with a factory header manifold. when i went to install it the flanges are different. the cat and the header flanges are turned in different directions. they are off about a inch or so. i was wondering if i needed a different header or just have a shop weld a new flange so they bolt up.

 

Go to a shop, it is an easy fix an shouldn cost too much, You already did all the work. A shop can cut the flange, extend the pipe if needed, and re use the stock flange