im using krylon Krylon ColorMaster Acrylic Crystal Clear, Flat spray paint over krylon supermaxx spray paint flat black on my car. im getting a dull greyish cloudy dull look. ive sanded it down and degreased it.

Simple 1k products....you are either seeing moisture blushing from the air itself or a solvent blush/reaction from the degreaser. Sounds like you don't have access to spray equipment here....would normally tell you just to take some lacquer thinner in a gun and "mist" over the area. That opens the coating up and allows the trapped moisture to evaporate.....

so a 2k clear wouldnt have this problem?

A 2k can have the same problem if there is still moisture/contamination trapped in the 1k you would put it over. In a 2k base/clear systems you just don't have the old moisture problems we used to run into with lacquers, etc.