Before everyone says it's impossible they are basically what giant says he is running (well the garret equivalents) and he's apparently making close to 400awkw's and has a 1/4 time of 10.2s run on RE55 semi-comps to back that up.
And I used to think giant was running -5's or something until I saw he's making 300kw's at 3,500rpm which you'd struggle to get with bigger turbo's.
So with the right set-up's, fuel and tuning it might be possible.