That is going to flow great!
The kit will outflow the turbo!
That looks about a 2.5" hole or so, if so; don't look back and move forward!
you'll see how linear and well it flows when you're done!

my kit on the avalanche wasn't exactly like that, the merge was between the turbo and flange, like a Y pipe (which yours is too); that big thing made 525hp on 11-12psi, Magnum 76mm, 48lb inj, walbro pump (stopped pushing it when fuel pressure started dropping), oh ya and the 6.0L i think, maybe the 5.3L i can't remember and don't care, lol.
Point is, you'll enjoy it.