Just found my dyno map which found its way folded up into a random folder since last Friday when my car was tuned. I remember seeing the drop off when I was there but didn't realise how bad it was, around 5500rpm it tumbles. Here's how my dyno run looks ...
IMG_20160810_074225.jpg
IMG_20160810_074241.jpg
First chart shows bhp against torque and second one shows bhp against boost.
I know the guy tuning it mentioned he was hearing knock which is why the boost was dropped down.
Any ideas what could be the cause of this big drop off?