This is a really common problem for VIN decoders on the Model S. Digit 8 in the VIN is specified as "4 = Dual motor - performance" (source: ftp://ftp.nhtsa.dot.gov/mfrmail/ORG11229.pdf) so any P85D or P90D will have that "4".
Anyone like Carfax, insurance companies, etc. doing VIN decoding will...