Most of the 2002 bikes need the upgrade just like the 03-05 bikes, but a few of the early bikes already have a high power amplifier in them.
Most of the 2001 bikes DO NOT need the upgrade. Only the very first 2001 bikes that came off the assembly line had low power amps in them. These early 2001 radios were actually the very worst of all the 01-05 radios. I have actually not seen one of the very early radios in quite some time, so many of them may already be retired.
Before I get into that procedure, here is a clue. If you have no audio through external speakers and have found through troubleshooting that the amp is blown, you probably don't need the amp upgrade. The weak low power amp puts out so little power that it never blows. Note that with my upgrade amp, I have only seen one of them fail in 12 years in business, and even that one lasted 8 years.
I have come up with a better, much easier way to determine whether your 01-02 radio needs the upgrade than the old procedure. The only thing you will need is a multimeter (voltmeter) and all you have to remove is the seat.
Note: For those that do not have a multimeter, you will have to remove the radio and check the serial number to determine whether it needs the upgrade. Email me the serial number at firstname.lastname@example.org and I will look it up and get back to you ASAP.
After removing the seat, look for a large rubber boot just to the rear of the relay box. This boot houses most of the connectors under the seat. Slide the boot back as much as you can, and look for a the white 4 pin speaker connector. If you don't have rear speakers, this connector won't have anything plugged into it.
Once you have located the connector, turn your ignition to the accessory position and turn the radio on, Make sure the radio is set to play through the external speakers. (Play some music through FM just to make sure.) After that, turn the volume all the way down so that the music does not interfere with your voltage measurement.
You can make your measurement on the back side of the connector or unplug the speaker harness and measure directly on the pins, whichever is easier for you.
Attach your negative meter probe on a known good ground. The negative battery post is a good place, or any metal part that you know is grounded.
Set your meter to measure DC volts. If your meter is not autoranging, set the dial at a low voltage range, such as 20 volts.
Now take your positive probe lead and measure each pin of the speaker connector. If you have one of the low power, high distortion amplifiers, the reading will be about 2.5-3 volts on each pin. If you have one of the higher power amps, the measurement will be around 5.5 to 6 volts.
That is all there is to it. If your measurements read the lower 2.5 to 3 volts, your amp needs the upgrade.
I will add some pictures of where the connector is at as soon as I get a chance