Corvette C7 SR Strange to tune?

Hi guys,
I’m having a complete nightmare tuning this car. I brought the pack for this car as I see someone set a blistering time on Road America a few days back.
I needed a good tune for Road America so I’d thought I’d give it ago. So far i can hit the low 02.09.000 which don’t seem to be good enough… My specific problem is I think down to the gearing the 7th gear seems to throw every thing out… I know how to gear a car on forza (well at least I did until now) I have the arch on the chart in the tuning section and it’s nice arch shape. The problem is that it seems to struggle getting the power down in places. Specifically in the 3rd to last corner and the last corner before the main straight.
I’m not very good with American Muscle and it don’t seem to rev that high so again a presume it’s all toque. Putting higher cams in don’t do it any justice what so ever it just revs and nothing comes of it. I’ve tried stiffening the ARB’s suspension and damping to no success. Anyone got any ideas on how I can just squeeze a few tenths out of this car?
Also I have tyre wear on for tuning just because it adds a little bit