It's mph and good going in a short wheelbase car in my opinion. You'd have to know the road and car, and have big brass balls to get that fast on a public road. I'm sure you know your abilities, but please stay safe.
My wife ran my modified FIAT Coupe 20vt off the 160mph clock once, I didn't have a GPS to verify and suspect the speedo ran fast, however, I'm not ashamed to admit I wasn't tough enough to do it.
I'm not condoning speeding or breaking the law, however, there are plenty more dangerous ways to get your kicks.