I've probably only seen a regular Buick GS, but I don't know about a GSX stage 1, so I'd say no. Have you ever seen a Chevrolet Corvette ZR1? I only saw one for 2 seconds but it was definitely eye-catching.
No. I have seen a Chevy 454 SS though. It's my favorite ever muscle truck. Have you ever seen a Volvo P1800ES?
No but I have old matchbox scale model that copies this car --- Post updated --- Have you ever seen a Dodge Omni?
Yes, in fact the same one multiple times (in a downtown area near my house)! Have you ever seen an Alfa Romeo Giulia Quadrifoglio?
Yes, it's a beautiful car! I saw one in yellow, it looked amazing! Have you ever seen a Ferrari 360 Challenge Stradale?
I've definitely seen a few F360's, but as to if any of them were Challenge cars I don't know, so probably no. Have you seen a new Renault Duster? (as I just saw one recently here in the US in this almost same exact spec but in orange, I'm guessing it was a Mexico market car).