Hello MBF, Yeah that's for sure an IFG body, I have one also, the 4 tell signs are...
1. the front parking lights are too far inward and not align with the headlights, 2. Yes! The rear deck lid is copied from an earlier year diablo and has the impression for the lamborghini script to fit in which should not be there but smooth like oem (I filled mine with glass btw) 3. the rear radiator grills are not wide enough like oem. And 4. the main rear air inlet scoops are too narrow.
Also you say it use to be silver? yeah IFG, But of course not many people would know or can tell these things. But sorry I don't know who built it though.