Not sure if everyone is up to speed on their TIG welding titanium knowledge, but if not here is what you need to know
It's difficult !! LOL
Both the outside and the inside of the weld must be purged with gas to do it properly
Here is an example of one of the very best around, Matt from (now) Absolute Motorsports working on the exit pipes (if you may recall, Matt did my 69' Camaro back in 2019)
See the capped end filling the pipe with gas
IMG_8603 by
Steve Heck, on Flickr
IMG_1608 by
Steve Heck, on Flickr
IMG_1585 by
Steve Heck, on Flickr