depending on what downpipe you have, and your setup, it is doable to not have to remove it. you pretty much want it past the bellmouth. iirc you have that txs dp, so look for the skiiniest part(about a foot +or-, you can 6" or closer hell) and that's a good spot for the bung. you ever see a downpipe that came with a bung there already? if you think someone could fit in there to weld, then stop in and ask. i can't see your clearance so it's hard to say.

the aem is a good gauge. if i went with one there are only 3 i'd even think of, and that's one.