There are two folders where these ini files are sitting. The SteamApps\common\assettocorsa\cfg and then under the Windows default Documents folder.
Did you change the race.ini under C:\Users\XXX\Documents\Assetto Corsa\cfg (win7)? If you did it should work then.
I haven't have time to put any considerable amount of driving hours in to Assetto Corsa, but I haven't seen a single penalty after doing this modification.
Lotus Evora is far and away the best car I've tried on Joux, the other Loti(Lotuses?) are too 'hard' but the Evora is perfect, feels like I'm blasting along a good B road, it's perfect.
Your 'old' 570 is still far better than most cards. My 'even whimpyer' 560 is still better than any of the new xbox or ps4 offerings, and so they should be !
PC graphics are still catching up with the hardware and the latest gear should kickass in any game for the next 4 or 5 years.
Did some testing in the 12c myself today with the following results:
TC = 2 and Stability 100% I achieved a 1:52:70 in about six laps, then
TC = 2 but with Stability Off I archived a 1:52:72 in about six laps again, then finally
TC Off Stability Off was able to hit a 1:52:87 but that was with a lot of effort probably about 20 laps or more with a lot more mistakes.
My general opinion on the various settings is that the TC is by far the most beneficial to confidence and lap times. I didn't like stability control much as it prevented rotation of the car when I was wanting and expecting it. TC without SC tended to allow me to use more of the track without getting into too much trouble while keeping a more neutral to over-steer balance.
With TC and SC off I found my concentration levels had to be amplified several fold really having to think constantly about where the grip was or wasn't with small mistakes costing much more than with TC on.
Surprisingly though SC and TC didn't net massively faster lap times out of the block but what they did do was make it easier to hit the target.
Stock setup except semi-slicks and 15 litres fuel. Challenging to keep rear tyres from over-heating. Excuse the love tap
Obviously room for improvement, next target is <6m05, such fun.