How is your engine running ( STS 28)?
Because if have also tryed that engine but I think it was to hard to keep in the right temp.
But now iam running the STS 21 With the red top, and WOOOW.
With af thunder tiger pipe i get almost as mush power as an RB WS7, but more time on the track before i need to pit... I get almost 11 min out of it. And most of the RB engines get maximum 8 min before they need to pit.