Според второто ограничение, когато се появи превозно средсво с вече въведена марка не го запазваме.  Въпреки това пак ми дава само 33/100

using System;
using System.Collections.Generic;

namespace _06._Vehicle_catalogue
{
    class Program
    {
        static void Main(string[] args)
        {
            string input = string.Empty;

            double carsHorsePower = 0;

            int carCount = 0;

            double trucksHorsePower = 0;

            int truckCount = 0;

            List<Vehicle> vechicles = new List<Vehicle>();

            List<string> brands = new List<string>();

            List<string> checkBrands = new List<string>();

            while ((input = Console.ReadLine()) != "End")
            {
                string[] tokens = input.Split(' ');

                if (checkBrands.Contains(tokens[1]))
                {
                    continue;
                }

                Vehicle vehicle = new Vehicle(tokens[0], tokens[1], tokens[2], double.Parse(tokens[3]));
                
                if (tokens[0] == "car")
                {
                    carsHorsePower += double.Parse(tokens[3]);

                    carCount++;

                    vechicles.Add(vehicle);
                }
                else if (tokens[0] == "truck")
                {
                    trucksHorsePower += double.Parse(tokens[3]);

                    truckCount++;

                    vechicles.Add(vehicle);
                }

                checkBrands.Add(tokens[1]);
            
            }

            input = Console.ReadLine();

            while (input != "Close the Catalogue")
            {
                brands.Add(input);

                input = Console.ReadLine();
            }

            for (int i = 0; i < brands.Count; i++)
            {
                foreach (Vehicle vehicle in vechicles)
                {
                    if (brands[i] == vehicle.Model)
                    {
                        Console.WriteLine($"Type: {System.Globalization.CultureInfo.CurrentCulture.TextInfo.ToTitleCase(vehicle.Type.ToLower())}\n" +
                           $"Model: {vehicle.Model}\n" +
                           $"Color: {vehicle.Color}\n" +
                           $"Horsepower: {vehicle.HorsePower}");
                    }
                }
            }

            Console.WriteLine($"Cars have average horsepower of: {carsHorsePower / carCount:F2}.");

            Console.WriteLine($"Trucks have average horsepower of: {trucksHorsePower / truckCount:F2}.");
        }
    }
    class Vehicle
    {
        public string Type { get; set; }
        public string Model { get; set; }
        public string Color { get; set; }
        public double HorsePower { get; set; }

        public Vehicle(string type, string model, string color, double horsePower)
        {
            Type = type;

            Model = model;

            Color = color;

            HorsePower = horsePower;
        }

    }
}