I just noticed that a bone stock Mitsubishi 1997 GTO (3000GT) RPMs do not match if you drive in cockpit view and you have the RPM gauge to the lower right screen, which is part of your HUD. I found this glitch or bug while driving on the Indianapolis Oval in Rivals. I recommend testing this for yourself along with other cars. I am interested what other people think and what they happen to discover as well…and hopefully we as a community can help Turn10 in the process 
Unfortunately it’s unlikely to be fixed just like many of the other ones unless its really game-breaking.
Yeah that is a bummer 
After further testing this with the telemetry, I believe the issue is the cockpit view shows the incorrect RPMs while assuming the telemetry is correct and the HUD RPM gauge in the lower right of the screen are correct. They seem to be a 1000 RPMs difference.