Some things to consider:
If a maximum HP number is set, say 135rwhp. Then won't we all be building to that number? Cars with more than that will figure out a way to reduce HP and increase Torque. Just another way to increase cost.
Adding a muffler may do just that. There will still be disparity.
There will still be those that think they should be able to win with 130hp but don't have the driving skills to accomplish that.
Can a 130 hp car win? YES it can. But not at the Nationals. It must be fully sorted, excellantly prepared, handling perfectly and driven well with premium tires to win the Nationals.
There is no substitute for track time. This where a driver who thinks he is being out spent should spend his money. Until you can turn laps within .3 of a second lap after lap HP will not get you to the winners circle.
The top 6-8 drivers at the Nationals are at this caliber. It takes years of practice and racing to get there.
This is where the largest discrepency is in 944Spec. It is in the driving ability. Look at the lap times from the Nationals. Look at the consistency from lap to lap of the leaders. HP will not overcome consistency. It takes the full package.
It is no surprise that the top cars/drivers have the best engines & setups.
If you come to the Nationals with anything less than the best (driver, car and prep) your chance for a podium finsih is reduced. That is called racing. Bring your best car, drive it well. Have FUN!!
But be realistic about your abilities and work on improving your driving at all times. Even the Best drivers in the world make small mistakes on every lap.