I used this tune (without SRF) that I found on gtplanet:
With SRF on it's probably a lot easier.
Good stuff, thanks.
It's weird that there are upgrades that lower the weight or increase the downforce, but don't increase the PP.
EDIT: Had a look at how much that tune would cost, thought 'fuck that!' so for the first time turned on SRF and the assists, bang, four seconds quicker, gold got, what a joke.