Well, you want to go fast in a strait line and you arent concerned about turning on a dime. That's what i wanted out of my nrs4 2 rtr. I spent over 1k on it. The biggest increase in speed was with a new engine and 2-speed. You mentioned you have a tuned pipe and 2-speed. That's great. Now you might want to consider a high rpm engine with good hp. Gearing and rpms is where speed is most gained or lost. If you want speed and just speed, then get you 2nd gear as tall(big clutchbell/small spur) as u can. If you go too tall, your engine will have trouble and take longer to reach speed and rpm. That is why you want you engine to have enough hp. This also applys to you 1st gear ratio. You want it to have nice accelaration and a smooth shift into 2nd gear. You might have to fool around with ratio to get it how you want it.
After you get a decent engine then see whats what. I, myself went wild on my nrs4 2. I bought all the graphite, lightwieght, and speed goodies i can get. My engine is a sts mt12 with a cvec pipe. If i was formilur with the rs4 3, then i could help ya more.
Wow these forums have gotten popular since 02!