The difference was immediately obvious. The car had real PEP. It was very difficult to keep it under 80 mph. The engine reved incredibly freely all the way to 7500 (until the rev limiter kicked in). You could feel it really breathing freely for the first time. The biggest difference was accelerating from 65 mph to 85 + mph. There was real power at high rpm. I was really pleased with the entire setup. I took the MCA's advice and advanced the timing to 14 degrees BTDC and felt an even bigger boost to the power. I was even more shocked when several of us took a trip to Lake Tahoe (6300 ft. with passes over 7000 + ft.). In previous trips with two different Miatas, the thinner air was immediately noticeable above 4000 ft.
The car wheezed and had no pickup. Now, with this intake system, the car really screamed even above 7000 ft. I could pass campers, and drive just like at sea level. This was a really spectacular improvement.
I would highly recommend this system to anyone who doesn't want to spend the money on a supercharger or turbocharger. There are no moving parts and the system is very well designed.
For additional oomph, I have since installed the Jackson Racing Chrome Header to complete the opening of the entire intake/exhaust system. These three pieces have a tremendously beneficial effect on the Miata's performance.