Let me add a few facts to this discussion...
Most motorcycles, and most car engines have a cooling system that operates between 180 F & 220 F.
The Z900RS has a warning light that comes on at 239 F, that's way too hot.
Most current engines in bikes & cars have thermostats that open 200 F / 210 F, and close at 170 F / 190 F. They can vary from that, but those are sort of normal numbers for smog engines.
The Z900RS thermostat opens at 144 F, fully open at 167 F, and closes at 131 F. The reason is that the bike has a fairly small radiator, because it's a retro styled bike.
The fan comes on at 212 F, and goes off at 208 F, which is way too high, by about 20 degrees, with very little temperature spread.
What all this means is that in heavy traffic, urban riding, low or no air flow through the radiator, it gets hot rather quickly, and the fan does not react, until it's pretty hot.
There is no doubt that when you have the ECU remapped for about $300.00 , they can, and do reset the fan to come on at a lower temp, which is good.
But, if you do not want to remove the Cat, and leave the stock exhaust system on the bike, a remapped ECU is pretty much not worth it, due to the narrow band O2 sensor, still in the system, with the PAIR air system.
Tonight I took a 25 mile ride to see how the fan switch worked in real life. Most of my 1700 miles of riding so far, the temperature bar system on the dash has been at 3 bars for normal riding, (70 f / 85 F outside air). If it's a cool night (55 F / 60 F), and I'm doing 70 mph, it at 2 bars. If I stop at lights in town it's 4 bars, if I get in heavy stop and go traffic in Milwaukee, it's 5 bars. I have seen 6 bars once in heavy traffic, on a 90 degree day, that's 1 off of the high temp light. The bottom line during my ride tonight is pretty simple, the fan switch drops the temps by one bar, or it will drop the 4 bar to 3 bar, 5 bar to 4 bar, etc. If I stopped at a light that was long, I would see the 4 bars go to 3 bars as I was sitting at the light. Pretty simple.
Now the down side...
They included a little blue LED to let you know that switch is turned on, makes sense. Holy crap in the LED bright. When it finally got dark, the light was just glaring at me. So, back in the shop, I took a black paint pen and put a drop on the top of the light, so all I see is what's around the sides. Problem fixed.
The bottom line, with the extra wire, etc, I have about $60.00 US invested in the whole deal, less my time, and it works good enough to leave it on the bike.
PS #1, Here's a day & night photo of the dash.
PS #2, look for my ad later this Fall for my new Titanium exhaust system that I am not going to use.