Take it off. If you weld when it is on, you will get some burn through and guess where that goes when you start the car. Sounds like a pop corn popper when it goes through the turbo. Trust me I know.
what if i welded it on and the take it off to get the metal out. does the header have to be attached to the head so it want warp and cause and exhaust leak
A lot of people say it does, but my friend did it completely "wrong" (not attached to anything, mig welded) and it is holding up fine after 6+ months. Bolted right back on because the heat got no where near the flange.
