Your top end speed is being limited by the PCM (computer). It can be changed by yourself using any number of hand held tuners, or by a professional tuner like Allen Nelson.

For a true HP "boost" (Power Adder) the main choices are forced induction, tubro or supercharger, cam, heads or Juice is by far the cheapest and easiest of these. Use it at your discretion.

On the flip side, there is plenty of HP you can get back, so to say, from the factory setup. It's not all about what's under the hood either. You have to look at the big picture, including gears, transmission, traction, etc. A bunch more HP/TQ does you no good if you can't efficiently get it to the pavement and not break your drive-train in the process.

Read through the previous posts here and/or use "search" and you will find some very useful information. As a start, not counting true Power Adders, my short list would be:

- PCM tune (Nelson Performance is preferred by most guys here)
- E-fans
- Exhaust
- Shift kit

Good luck.