I'm pretty sure that's him, to date you make only 3 of us that converted over and I don't expect more with the HPT new Turbo exhaust housings.
Your turbo while only a 68/62 Max's out at maybe 1050hp but your exhaust housing will chip away at that number.
.83 housing to 1.01 only looks to be a 3lb/min flow difference, not as big of a choke as on my 770 turbo. If you're looking for say 900hp and 1000tq etc you can get that on the .83 it looks like with a 250rpm spool difference vs 1.01 for the street. These really hit hard in our engines 3500-4500 torque range with a great converter.
What housing, T4 or V Band and size?
Some things for discussion to consider.
I don’t know if the dyno you were on is able to control the load or loading rate. While the new Garrett turbo is definitely superior to the old TA-49, it looks like the TA-49 did not get to full speed until 4800rpm. If the dyno allowed the speed to climb at the same speed rate then clearly the new unit is superior in response. It would be interesting though to hold the rpm at say 500 rpm increments and let both turbos peak prior to allowing the speed to increase.
As far as the housing flow chart for a specific wheel, it does not really tell the story. I have not been able to make heads or tails of turbine data. Compressor data/maps are easy and straight forward, the turbine data is not. So as an example, the chart posted shows turbine data for a set of housings, though the mass flow presented is not enough to make the boost we are running at the mass flows we are running, even for small compressors. Case in point, using the .74 efficiency and a generous temperature drop, the shaft horsepower for given flows is approximately shown in the chart below:
If you look at the BW match bot, the compressor power required for a similar car presented here, the flow above would not produce enough shaft power, even with the largest housing. The moral of the story, the turbines are not operated at their best efficiency points, they are operated at the point (requisite pressure ratio) to make enough shaft power to produce the desired boost. Since exhaust is wasted energy, the only point that matters is the back pressure required to make the shaft horsepower to generate the desired boost. Increase in turbine pressure ratio equals increased pumping losses. It is the trade off to meet the desired performance.
It is difficult to use the turbine charts to match up to a car, where the compressor maps are much easier to match to your car. The other thing is trying to match the compressor and turbine speeds. It seems the vendors keep the turbine data more concealed than the compressor data.