Yeah, funny how 130-133 whp used to be a strong engine, and now the guy with 137 whp is the one at a disadvantage. These cars only came with 150-160 hp at the crank from the factory, so you really have to ask "what gives!?" with some of the higher numbers measured at the wheels. Do they magically have less drivetrain loss than everyone else, or are they just putting out way more crank HP than a brand new 944 ever did?
Ram Air: I don't see the problem, so long as the car isn't cut up to accommodate it... It's dirt cheap, obvious, and easily available to everyone. Restrict it and you'll just reward those who are turning this into a builder's class, since they'll test to find the coolest and highest pressure spot to draw air from, while other people wont go to such silly extremes. Let it remain legal and then everyone has easy access to it, not just the few who spend R&D time. If we're going to bring the dyno into this, then just ensure that the fan isn't pointed at the air intake.
Claimer Rule: I like the idea, but foresee problems with figuring out the dollar amount, the logistics of it, and people actually using it. I think $4000 is too high for a 944 engine, but expect politics and other drama to prevent anyone from actually utilizing it if it were to become our rule.
HP vs weight: YES, and make torque a factor too! If it's only WHP alone, then you can manipulate intake and exhaust restrictions to give you a bunch of torque while still being under the WHP limit. Torque matters more anyway.
If your car is X whp or torque over the baseline number for the class, then you must run a higher minimum weight, which gets you back to around the same power-to-weight ratio as the baseline. Power-to-weight isn't everything, because the heavier car (ie the higher HP car) will still be faster at higher speeds, but it also has to brake and turn with that weight, which can make it an overall disadvantage. Give the higher power cars some meaningful extra weight and people wont be building silly engines like an arms race anymore, because it will be a weight advantage to have an engine that makes only the baseline whp and torque.
We'll never make everyone's engine the same, but if there's going to be an advantage, it only makes sense to give it to the kind of low-cost nothing-special engine that the majority of our class already has. Make the inexpensive, easily obtainable, engine become the one everyone wants. I'm talking about low compression pistons (which is the overwhelming majority of NA 944 engines), the head isn't shaved to the max, and the valves and rings are still good enough to have a decent seal. In other words, something that you could find in a 944 junkyard.
Restrictor plates: No... too easy to game these. They restrict top-end and peak whp numbers, but torque at corner-exit is far more important and isn't really affected by the restrictor. Spec Miata runs restrictors on some of the engines too, but people still dump stupid amounts of money into building them.
Anyone who does not have the skills to build the motor at home has a "pro built" motor. 
