Anyone else have problems at highspeeds?

Hemingway

OP how many miles have you driven your Z? Prior to getting my Z, I was driving a 2014 Honda pilot(which has john deere tractor steering feel). When I first got the Z, the car felt super twitchy, I was holding on to the wheel with 2 hands afraid the car was gonna veer off the highway from a tiny bump in the road. Long story short, you may be overcorrecting. It took me at least 3-4 thousand miles to get fully adjusted to the Z. If you find no mechanical issues with your car this could be your problem. Follow the other members advice 1st...check tire pressure, alignment, have a competent mechanic check the car out.