Heres the tune I used for the GTR tuned TT.
I only fitted reversible upgrades.(as with all these TT's)
I think its mostly L.Hamiltons but with altered gearing(You might want to shorten the final ratio).
Good enough for a 50s after a few laps.
As I said give the credit to Lewis Hamilton for this set-up,hope it helps.
EDIT:I inputted the front ride height wrong on my car
Its still good for the times but if you like your car more pointy raise it to +20.👍
How did you get the gearbox with those values, mine is no were near that values(MPH or KMH)