Changing elbows for aftermarket should allow slightly better flow and exhaust efficiency. You may also see slightly faster spool up but I'd suggest this would be negligible. At the level of tune your talking I'd suggest spending your cash elsewhere unless you can get a very good deal on a new or used one!!
I got R34 ones which are supposed to flow a bit better than my original R32 ones and not prone to cracking as some after market stuff suffers. Whether it made a difference I couldn't say as changed turbos at same time