Just out of interest, it isn't a Hei Hei, it's a King Kahuna. The Hei Hei didn't have the gussets on the top and down tubes.
1997 King Kahunas had the same Hei Hei decals on the top tube as the Hei Hei, but it also said King Kahuna in lower case script on the seat stays, and those seat stay decals have presumably come off on your example.
The King Kahuna frames sold for £300 more than the Hei Hei, but nevertheless attracted the great majority of sales, as they were perceived to be 'better'. That may be a matter of taste, but they are slightly stiffer and heavier than the Hei Hei, so certainly better for racing.
Edit
I'm sorry, I've just noticed that you already said that!