Maybe it isn't I really don't know. I just looked it up to see what I could find. It did seem weird that the Porsche was that much slower, ive heard a lot of people say it shouldn't be. So I was just trying to find a logical answer. 👍
Edit: everywhere I find specs for the car, they have it as 1998-1999 GT-one. So it looks like the power plant and Hp was identical between the two years. According to this picture from the article, it does look like the GT-One was a bit faster then the Porsche:
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