[iggy1]

Its forplayerid not playerid.

EDIT: this is another method like what you want.

pawn Код:

public OnPlayerEnterVehicle(playerid, vehicleid, ispassenger)
{
    if(!IsPlayerAdmin(playerid) && GetVehicleModel(vehicleid) == 520)
    {
        RemovePlayerFromVehicle(playerid);
        SendClientMessage(playerid, 0xff0000FF, "You are not admin.");
    }
    return 1;
}