Can anything be done to increase the performance of the RX-8 Renesis Engine? (see below)

Unlike previous mass-production rotary engines, which employed side intake ports and peripheral exhaust ports, the naturally aspirated RENESIS has intake and exhaust ports in the side housings. This configuration eliminates overlap between the opening of the intake and exhaust ports, enhancing combustion efficiency. The intake ports are 30% larger and their timing has been changed to make them open sooner than in previous designs. Moreover, the exhaust ports open later, resulting in a longer power (expansion) stroke and providing radically improved heat efficiency.

At the same time, the RENESIS uses a six-port induction (6PI) design, in which each rotor employs three intake ports, and a variable intake timing mechanism. Under this system, dedicated high-speed intake ports begin to operate when the engine operates at high-rev levels. This makes it possible to use the intake's dynamic effect at high and low speeds to maximize compression efficiency.

Unlike the single peripheral port per rotor of previous designs, the RENESIS uses two exhaust ports per rotor. This produces a combined exhaust port opening area nearly twice as large and results in a substantial reduction in exhaust resistance.

The rotors have also been made lighter for better performance at high-rev levels. The rotors used in the RENESIS weigh approximately 14% less than those used in the engine that powered the 1993-2000 Mazda RX-7.
These enhancements provide high output rivaling the power of turbocharged rotary engines with linear power characteristics from the low- to the high-rev range.

What can be done?

Well, this is what I have added to my 2004 RX-8 so far :

Cold Intake System SR Motorsports

Underdrive Power Pulley

Greddy Catback Exhaust

SR Motorsports High Flow Cat

The car now has a 27+ horsepower increase.