Its because Luke forgot to upgrade the common.erp file with the mercedes.vft.xml I sent him in the Mod.
Thats because the Mercedes car has no own xml file. Sorry 4 that I didn't tell him properly.
The common.erp file has to be put into /asset_groups/f1_2018_vehicle_package/teams.
Until the update in the Mod you can download it from here.
drive.google.com
Just replace the common erp and it will be allright.
The Ferrari Performance should depend on the track. In my Simulation in Bahrain Ferrari was on Pos. 7 and 9. In Real Life they were on 6 and 8.
In 3 of 4 Races in Real Life Ferrari had slower fastest-laps than Mclaren so I put them slightly behind them in performance. Maybe I will update it if nessessary after the next races.