I've run 'blued' 090s at a Cadwell trackday and had no problems at all. Like the article that max posted the tyres look normal after the first session and they were fine all that day and the first Llandow trackday as well, changed em after that though.

I hav a set of 090s on that have done one day at Dono and I am hoping (maybe in vain) that they are gonna last me at least another 3 trackdays this year.
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MC21SP - Roth-tax
CBR400 - track
MC21R - sold
MC21SP - sold