Here's the procedure.
First you must disconnect two sensors (presumably RPM limiters?) from the tranny. One is the fourth gear sensor, while the other is the fifth gear sensor. If you look at the transmission under the car there are supposedly four (4) sensors (I only saw three, but the fourth one is somewhere under there), the ones that need to be disconnected are the middle two (2). The electrical connections are simple snap lock configured so not cutting is required. Once the two connections are disconnected, I recommend you thoroughly tape over the ends of the connectors to prevent moisture from entering within.

By doing this step the ECU doesn't know your 4th or 5th gear RPMs, therefore it won't limit you. Note: If you have faith in placing your car on jack stands (some members have done this) you can test the limiter for each gear before and after each step. What you'll find is that the ECU limits the top end RPM for 4th and 5th gear before you disconnect anything. Afterwards, the skies the limit.

The last step is to disconnect a control wire that comes from the tranny area and passes by the passenger side of the starter in the engine compartment. You'll find another simple electrical connection (looks like a tube style fuse holder) with small gauge wire. Unhook this connection and then drive your car and you'll notice the speedometer doesn't work, nor do the number onyour odometer change. What you've disconnected is the sensor that transmits the speed to the ECU and the display. Now the computer tries to watch your speed to make sure you don't go past 180kmh (S13 model, S14 may vary higher), but never cuts off your fuel since it doesn't have a clue how fast you're traveling.

Since most of us don't cruise over 180kmh you may want to wire a switch into the speedo connection just mentioned. I used a simple red rocker switch and installed it into the blank Nissan console plate located to the right of my
rear window washer/wiper control buttons