Sooo, I play with a controller rather than a wheel, so what I say here may not be applicable.
Firstly, New York isn't actually the best cash grinding event. That honor goes to the Uber Dam event. Main Highlands Cave is also a solid event to grind cash. If your JetSprint boat is at max rank and you run the race at ACE difficulty, you can potentially make a minimum of $18.9k every 90 seconds.
Secondly, The Crew 2 subreddit/Discord server has put together
this spreadsheet of user-made vehicle tunes. It has some solid Hypercar tunes (as well as tunes for almost every other vehicle) so I'd recommend starting there. Generally speaking, I prefer to use the tunes created by Akorr, as his tunes tend to focus on overall maneuverability, but lack some stability depending on the car. I've found that most cars in TC2 tend to be biased towards understeer, so his tunes help a lot.
For Hypercars, My general rule was one of "the faster I go, the slower my steering has to be." Once you get past 240 mph or so, you really need to be somewhat slow and deliberate with your steering inputs. Trying to change direction too many times at speed can unsettle the car and cause it to fishtail. You also want to make an effort to look ahead into the horizon as well. The game will generally spawn traffic cars far enough ahead to where you should be able to see them coming on a flat road, so try and watch the traffic patterns. Instead of trying to dart between traffic cars, get on the shoulder when possible, etc. Hypercars can also get on two wheels rather easily, so be mindful of that. In those scenarios, try to lower throttle a bit. Sometimes it helps, sometimes you'll still go for a ride.
As far as dealing with the New York race (I'm assuming you're still on the Normal difficulty?), what I did was complete every other race get my Hypercar to 320 before giving that event a real go. Because of the performance discrepancy between yourself and the AI, chances are that on Normal and Hard difficulty you'll pull away rather quickly from the opposition. This may result in a bit of a boring race, but at the very least you'll be able to get a hang of the route without too much chance of the AI catching up to you. Give it a run or two, and once you get a hang for it try it on a higher difficulty. If you're able to get your speed up quickly, keep it clean and build some space, you'll eventually get to a point where the game stops rubber-banding the AI. Whenever I do New York on ACE, I usually finish at least 2 minutes ahead of the next car.
What car(s) are you using and what's their performance rating? If you're at least Icon 1 and can put the cash and cars together, I recommend giving this weeks Live Summit a go. The platinum prize is a full set of Hypercar parts with affixes to get double loot that's also of higher quality. Car parts from Live Summit prizes (not the individual races in the Summit) will be at max rank for their category. When using the full set, any loot parts from events will be doubled in quantity, and have the best-possible chance of being higher-quality parts (Depending on the difficulty). These loot parts will also be at rank 320, making it easier to build up any other Hypercars you own. Since there isn't a car up for grabs this week, chances are that the competition will be a lot less intense, too.
Hope my wall of text helped!
for the tips, the spreadsheet, and the wall of text 
.
Will have a go tonight.
