I really find it hard to believe that a turbo of that size would hold back on your size engine. Which header/manifold are you running? You say it spools quick, what RPM does it spool at? That turbo should be good for around 900 hp. But with the MPH you are getting I think you may be already pushing it to the limits. At the most another 50 to 75 hp may be made, but that depends on many things also. Have you ever ran a backpressure test to see how much back pressure you have in the exhaust when making a pass.
I had thought that the .81 A/R is what that turbo came with, but I guess it could be ordered with the .70 A/R. If it does have the .70, then going to the .81 could free up some more power. Header & wastegate design could also gain more. I dont know what compression your engine is, but if it is below 9 to 1 you might even bumb the CR up 1/2 a piont to make more out of what is there already. Which intercooler you running?
Is your car a all wheel drive? If so this could indicate that you may already have the turbo at its max. It takes more power to drive the AWD and that may have my figures off on what HP I think you are making. If its a front wheel drive then you will be making less HP than I figure.
Anyway, a little more detail on the combo could help. A little maximizing here and there may bring more out of it. Or you may be at the piont that stepping up the turbo size will be needed.
Jess
