This is a very nice mod, I recommend having a go. I'd say it has one of the best engine sound FX in Assetto.
You can get it here: http://www.racedepartment.com/downloads/mazda-787b.4608/
(http://cloud-4.steampowered.com/ugc/537384367086421578/739820211360049B77EF5BE738044E03AC0836E6/)
(http://cloud-4.steampowered.com/ugc/537384367086406438/EFF37590A5C8BD98B4F1D5F134E536D9A1DA40A2/)
Oh yes, there is also a Christmas track now..... :) http://www.racedepartment.com/downloads/snoval.4566/
(http://cloud-4.steampowered.com/ugc/537384367086561411/76F7C96FA804766E284935DAE0F8B32EC9B0A623/)