I agree with Apostle, sounds like a primer problem. When I got my 944 repainted black the same thing w/ the rough greyish spots happened to me. Soon after those appeared the paint on the rear quarter pannels started to crack into a spider web pattern. Turns out the shop used half a can of old primer when they did the hood area (hence the paint not sticking properly) and on top of that the job was split between two different guys so the rear pannels got F'ed up too. The shop owner paid to have it redone at another guy's hotrod shop that was alot more expensive. I ended up with a custom shade of blackpearl and a flawless paint job for $850. MAKE THEM REDO IT and maybe you'll make out as good as I did.