Just a few thoughts...Why is it that racers feel like they have to run the same wind motor that the last world champion ran? Have we also forgotten how gifted guys like Rheinard and Hagberg are? Just because they can drive a car with a 4.5 doesn't mean you can, or potentially should. The beauty of mod is that you CAN run a 6.5 that us mortals can handle and still be in the same class as a guy with a 3.5. The difference in horsepower between a 4.0T and a 6.5T, on a standard sized track is negligible at best.
Also comes down to the "instant gratification" competitors want today. Mod is not a beginners class and should be something that you need to work up to. So fast stock guys jump up in class and can't win with a mod car, and lose interest. Is this a problem of the rules/class or a problem that the driver isn't willing to put in the time? Don't ask me what the solution is to the second point because I don't have the answer.