using System;
using System.Text.RegularExpressions;
public class Test
{
    public static void Main()
    {   
        string text = "VAL_ 344 PedalPos 0.0 \"% (0.0 ... 100.0)\" 100.5 \"Invalid - Undefined (100.5 ... 127.5)\";";
        var re = new Regex(@"VAL_\s*\d+|""[^""]+""|(\d+(?:\.\d+)?)", RegexOptions.IgnoreCase);
        var textmatches = re.Matches(text);
        Console.WriteLine("Result:");
        foreach (Match match in textmatches)
        {
            Console.WriteLine(match.Groups[1].Value);
        }
    }
}