v4 must be used with Pure v0.203+ and Pure Planner. Download and unpack the json-file in C:\Program Files (x86)\Steam\steamapps\common\assettocorsa\extension\config-ext\PurePlanner\Plans\Stamp and import in Pure Planner app or assign in session Weather-pulldown.
I made a couple of adjustments in track wetness when extended physics is used. Don't even think about starting the race without wets. You can change to slicks after 1,5 hour.