You are dreaming ........ a TT auto is not capable of reaching 6550 rpm in overdrive Assuming you were able to manage to do the impossible, you would be doing a theoretical speed of a smidgeon over 304km/hr
Actually, the OMNI on-line calculator using 64.9 cm on-road tyre diameter and the J-Spec TX ratios is pretty close.
I'm guessing here but either your tailshaft has broken or your transmission is fuct or you're funning with us If not, go you just - GO YOU!
According to my calculator I did in excel. At the given RPM and Overdrive (0.694) using 225/50/16 tires with Turbo diff gives 303.99 kph. The Non Turbo diff gives 274.88kph.
None of the above Mick. There is quite a personal and technical story here but I am not going to post it due to the inevitable pile-on from the doubters and naysayers, although comments about their experience from anyone who has driven a car at serious high speed, >200kph, road or track, would be welcome. I can say that my high speed driving and accident avoidance training was carried out formally over 4 days, by an NT Highway Patrol officer at the Hidden Valley racetrack in Darwin who boasted that he regularly averaged >150kph between Alice Springs and Darwin.