My mate used to own this car (rsoc member), I went with him when he bought it off another member. Was a well known car on that forum. He sold it to his mate who I don't think knows much about cosworths but was impressed with the condition an performance.
There is a printout for 433bhp from nms who mapped it but obviously at the flywheel lol. I believe he did comment on the turbo being either tired or pushed to the limits or something (been a while since I read it).
I still thought the figures was high for the mods even for flywheel figure. Does pull really hard though an is a stunning car! I mot'd it