Around the 130 range in an '85 Toy Supra on I-90 between Seattle and Spokane. Nice and smooth, just not enough power for the weight of the car
I had an RX-7 up to around 95 on I-90 in Spokane once, but it felt like it was going to pull off the road and flip on me, so I let up and didn't push it any further. Last time I try that crap in a featherweight of a car.
Have been 130+ as a passenger in my ex-roommate's '84 300ZX and it was smooth as glass and there was still power left (that was between Leavenworth & Wenatchee, WA).
Last May, I had my former Toy 4x4 V6 up to 103 on I-90 in Montana. That was about as far as I think I could get it to go. Ran out of straight stretch to find out. Toy 4x4 isn't exactly a cornering machine.
Now I'm in Japan, so even if I got my Toyota Ceres up to speed, it wouldn't be much because everything here is governed