Donington Race 2 Telemetry

I know I have not posted a report of the races yet but in prep for Snetterton I need to try and work out why my car was not pulling well at the top end of the back straight. In all but the first lap of the second race I was about 10mph down on my normal speeds on the back straight.
strangely the peek speeds elsewhere on the laps were fine, 122 down the craners for example but it would seem to be just what happens when I get into 6th at the end of the lap.
When we get around to lap 5 the problem is even worse.