Well, with a stock 60 A.R. compressor and a .48 turbine, it starts maxing out around 280 rwhp.
You can push 300 RWHP out of a 60/.63, but that's about it.
If you hit 250 rwhp, it's better to just upgrade to a larger unit from there.
The key here is remembering your "pushing" your stock turbo when your closing in on 300rwhp.
A proper sized turbo for 300rwhp would meerly be lounge'n about with an iced tea , where as a stock t3 would be huffing and puffing like a 40 year smoker on his 8th pack for the day.
Being done, and being done right are two differnt things