Fantastic results as ever from Bill and Alex. Don't get hung up on the 770bhp that Garret rate the turbo at. You could theoretically get 770bhp out of this if it was on a larger engine that was more efficient than the 1.8T (High compression with direct fuel injection etc etc) and running on E85. Maybe something like a 2.5 TFSI .
If you look at the compressor map you can see that the G30-770 doesn't do that well at high boost compared to some of the BW offerings but it's a great turbo in terms of size and packaging to fit in the limited space available on the S3. In the real world over 600bhp available from 6000rpm onwards is massive. The peak numbers are nice to talk about but it's the area under the curve that really matters.
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If you look at a 750bhp rated turbo from BW something like the 8364 that has an almost vertical line at the right hand side of the map that extends upto around P2C ratio of 3.2 which is around 2 bar of boost and then carries on up a lot higher than the Garret turbos. It will support over 3 bar of boost and still give you over 70Lbs/min of air.
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I strongly recommend you look at a CSF radiator though if you intend to take it on track. You have an intercooler which is optimised to reduce pressure drop by having more passageways across the intercooler so results in less flow through the rad. In my experience of track days with a standard rad and only 500bhp with a more free flowing intercooler and no air con rad you will struggle especially in the summer.
Really funny what some tuners are doing on these car with a G30-770 and a similar build to yours.Running 2.4 - 2.5 bar boost so the turbo is well outside it's design speed. It will live there for a while but it's not sustainable, but then a lot of people only see the numbers and don't think about how long it might last.
we haven’t twisted that arm of yours enough yet? 
This is crazy,251bhp more than previous setup.
