same issue with me, and to test it I redownloaded a fresh copy from Rockstar, installed LSPDFR and then added the LML and Coastal Callouts, instant lag spikes/stuttering, removed the Version.DLL file and all was fine, put it back and same thing occured,
For now I remove the Version.dll file when I want to play LSPDFR as normal, but have to put it back when I play Coastal Callouts and live with the lag