mrmcmo

Thank you so much for your answer. You did indeed solve the porblem. 
 
Thank you again!!!!

You likely need to add a carvariations.meta entry for police2 in mpluxe2's dlc.rpf.
This is what you'd add specifically:
This is most likely correct but it depends on the model, as it's hard to say with a Federal Signal lightbar as that's pretty generic, as it could also be sirenSettings 2 or 13 among others.
If that doesn't work, you may want to link the vehicle mod you're trying to install and/or a screenshot of the issue.