I believe your warranty is about to expire if it hasn't already. Why did you choose to touch the stock turbos when you could make a complete kit with another set of larger turbos? Especially after seeing a few fail at doing what you're attempting.
Yes waiting for an exhaust manifold to be made and running piping around would take a couple days longer than what you are doing now. But doing that would be a guaranteed improvement and give you more overhead plus doing a legit/complete job. Doing so also might give you the chance to break ASR dyno numbers.