Well a buddy of mine bought this up pipe for his 09' WRX and it came with a flange for a 44mm tial wastegate. He bought a wyntomn wastegate and of course the flanges were different. So we used a hack saw to saw off the old flange at the welds and I decided I would weld on the new flange for him.
The machine was running at about 70 amps with about 10-20 pulses a second. Here are some pictures during the process.
Here is a picture of the up pipe with the old flange cut off and the new flange to be welded on.
Here are a couple pictures of the final product.