I recently purchased my first infiniti, it's an g37xs 2012 in very pristine condition, I am 52 years old and mainly do interstate driving back and forth to work, I have noticed this car has Hotchkiss front and rear sway bars, and a strut Tower brace. Previous owner just replaced lower control arms with bushings. I put brand new Bridgestone all season potenza 980 as tires on the car, had alignment checked, and nothing can be found wrong. The car is all over the interstate at 70 miles an hour, and with a cross wind it's way worse, the car has been inspected front to back by a reputable suspension shop and nothing can be found. Could it be the sway bars are off on their settings it is very hypersensitive on the steering. Any help would be greatly appreciated

 

Could be the new tires. Drive it a bit for 500 miles and see if it improves. I’m on my second set of continental dws06+ and initially it is twitchy, and would wonder around a lot more. After a few hundred miles it drives like normal. But, the steering wheel is pretty sensitive on these cars.

 

@Oldguydailydrvr
Most cars from the factory come with some understeer dialed in as the average driver can control the car in emergency situations when the rear wheels feel like they sit "inside" the front wheels of the vehicle (this is the analogy I use to understand), creating a plowing to one side or nose diving effect. FWD cars do this inherently since the drive wheels sit in the front. If you ever travel for work and drive rentals, you will experience this effect excessively on low end FWD economy cars with decent power. Nail the gas and the car feels like it wants to pull hard to one side.

Our cars are of course RWD or AWD, so we have the ability to change the stiffness of the swaybars in the front and rear to minimize understeer, even create excessive oversteering as rear wheels feel like they sit "outside" the front wheels of the vehicle, allowing the tail end to swing out easily. The RWD G comes with some understeer dialed in, slightly more on AWD since driving in inclement weather is prioritized over performance. Coupes and RWD Sport sedans have the least of the group and start out slightly understeered then get to a nice balance of over/understeer as you push the car. Lower the car, push the wheels out slightly and minimize flex through various forms of bracing, the car feels planted, which is why I never went the Sway Bar route (I'm older as well).

My sister used to have a later 90s era Mustang GT and that thing was tuned for oversteer and fun to drive, but you had to get used to driving it because the rear would kick out very easily, especially in bad weather where the tires are less effective.

Are you on the softest setting of the bars you purchased? Soften the rear if you can and see if that helps. You also can make the front stiffer and leave the rear alone, but I don't recall which brands are adjustable in the front. Lots of options and information online about how to tune this front/rear weight on the tires relationship to your liking.

I like this guys approach to explaining things, but there are dozens of others:

 

I'm going to say a combination of the tires not having enough dry traction but mostly the strut brace. I took mine off as I noticed what you did. I had Goodyear Eagle Exhilarate all around and the try traction isn't the best for a rwd car with 348 horses. It was scary changing lanes sometimes. Got some BF Goodrich g-Force Comp-2 A/S Plus tires in the front now, as I'm waiting for the rears to wear out, and got rid of the strut brace and no more twitching.