I tried the DMVLA4 vinyl by Intelicoat and had very good results, but that was with using APS, so I don't know if that is the difference, or if you are doing something different. Did the colors look desaturated in the test pattern when you profiled, or just in your final print? What application are you printing with, and what are the settings you chose? I used application driven color management and printed with the new profile from Photoshop CS3.
-Ron H.