Is using a backing plate an option? That would take a lot of the sugaring out of the equation on the back side, because that should probably be back purged if you're doing a butt weld with a gap like that.
Keep yourself moving, and do the same thing every time. It's like a ritual, if you do the same thing.. puddle, fill rod, move, puddle fill rod move.. it will look the same.
You can see bluing from the heat on the exhaust I welded are pretty even, consistent travel speed is key.