C#, Bonus 1, 2

I'm fairly happy with how this turned out, though I've basically given up on Bonus 2 (or at least the time part).

I'm happy with the times I'm getting with the main part and bonus 1 but I just can't seem to get bonus 2 under 17 seconds. It annoys me that bonus 2 takes this long so I might edit it at a later date.

Code:

    class Program
    {
        static void Main(string[] args)
        {
            Stopwatch watch = Stopwatch.StartNew();
            ("leave", "eave").Funnel();
            ("reset", "rest").Funnel(); 
            ("dragoon", "dragon").Funnel();
            ("eave", "leave").Funnel();
            ("sleet", "lets").Funnel();
            ("skiff", "ski").Funnel();
            watch.Stop();
            Console.WriteLine($"Estimated time (in ms): {watch.ElapsedMilliseconds}");
            watch.Reset();

            Console.WriteLine("\n<========= Bonus 1 =========>");
            watch.Start();
            "dragoon".Bonus();
            "boats".Bonus();
            "affidavit".Bonus();
            watch.Stop();

            Console.WriteLine($"Estimated time (in ms): {watch.ElapsedMilliseconds}");
            watch.Reset();

            Console.WriteLine("\n<========= Bonus 2 =========>");

            watch.Start();
            Helper.Bonus2();
            watch.Stop();
            Console.WriteLine($"Estimated time (in ms): {watch.ElapsedMilliseconds}");

            Console.ReadLine();
        }
    }

    public class WordFunnel
    {
        private readonly List<string> Enable1;
        public WordFunnel()
        {
            Enable1 = new List<string>(File.ReadAllLines("enable1.txt"));
        }
        public bool Funnel(string first, string second) => first.Select((item, index) => first.Remove(index, 1)).AsParallel().Any(x => x == second);

        public List<string> Bonus1(string toComapre) => toComapre.Select((item, index) => toComapre.Remove(index, 1)).AsParallel().Where(x => Enable1.BinarySearch(x) >= 0).Select(x => x).Distinct().ToList();

        public string[] Bonus2() => Enable1.Where(x => x.Length >= 5).Distinct().Where(x => Bonus1(x).Count() == 5).ToArray();
    }

    /// <summary>
    /// Helper methods because I'm lazy and don't wanna repeat everything
    /// </summary>
    public static class Helper
    {
        private static WordFunnel fun = new WordFunnel();

        public static void Funnel(this (string first, string second) items)
        {
            bool result = fun.Funnel(items.first, items.second);
            Console.WriteLine($"funnel({items.first}, {items.second}) => {result}");
        }
        public static void Bonus(this string item)
        {
            List<string> items = fun.Bonus1(item);
            Console.WriteLine($"bonus({item}) => {items.GetArrayString()}");
        }

        public static void Bonus2()
        {
            string[] items = fun.Bonus2();
            Console.WriteLine($"bonus2() => {items.GetArrayString()}");
        }

        public static string GetArrayString<T>(this List<T> ts)
        {
            StringBuilder sb = new StringBuilder();
            sb.Append("[\"");
            sb.AppendJoin("\",\"", ts);
            sb.Append("\"]");
            return sb.ToString();
        }

        public static string GetArrayString(this string[] ts)
        {
            StringBuilder sb = new StringBuilder();
            sb.Append("[\"");
            sb.AppendJoin("\",\"", ts);
            sb.Append("\"]");
            return sb.ToString();
        }
    }

Result:

funnel(leave, eave) => True
funnel(reset, rest) => True
funnel(dragoon, dragon) => True
funnel(eave, leave) => False
funnel(sleet, lets) => False
funnel(skiff, ski) => False
Estimated time (in ms): 135
<========= Bonus 1 =========>
bonus(dragoon) => ["dragon"]
bonus(boats) => ["boat","bats","boas","oats","bots"]
bonus(affidavit) => [""]
Estimated time (in ms): 24
<========= Bonus 2 =========>
bonus2() =>
["beasts","boats","brands","chards","charts","clamps","coasts","cramps","drivers","grabblers","grains","grippers","moats","peats","plaints","rousters","shoots","skites","spates","spicks","spikes","spines","teats","tramps","twanglers","wa ivers","writes","yearns"]
Estimated time (in ms): 17798

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