I just put dual Fiaam Horns on today the High/Low, 132 decibels each, the front plastic bumper cover was easy to remove.
I may just pull that off when i install my fog lights. I made a wire harness out of 14 ga. wire and soldered all connections except 2ea they were double crimped.
You can just as easily crimp all connections, and it will be fine as long as they are good crimps, I did a pull test on each crimp.
I have a wiring diagram, that I used i wanted upload it as it may come in handy for someone else. It is not in the format that i currently use, for manipulating pictures.
The wiring diagram shows direct Fused power from the battery, into a Relay.
DO NOT wire your Dual loud Horns Without USING A RELAY, you will over heat your wiring and melt the insulation off as my horns say that they draw 4amps, that is a lot, with a relay it is .2 amps 2/10s of a amp. This method will save your wiring/electrical system.
Your horn will be louder wiring them direct to the Battery and using a relay. Safer too.
Especially the tiny wire that they use for the stock IQ horn it looks like 22ga wire it is very small. I used 14ga. from the horns power side to the battery, and 16ga on everything else. They are LOUD!!! the dual high/low sound is very European sounding.
If i can figure out how to up load that wiring harness diagram i will. Update: Uploaded schematic/wiring diagram
The IQ is a little different than the diagram as all grounds can go to a good ground, ie; to a bolt somewhere on the chassis. Like #86 on the relay (see diagram) and the ground on the horns, as there is only one wire on the stock horn it is a + positive wire going to #85 on the relay.
Wires #87 & #30 on the Relay were the 14ga wire, all others wires were 16ga.
hopefully this explains the wiring and is easy to understand.
I did this on a couple of motorcycles that I put the same Dual Fiaam horns on and they are LOUD people do not expect to here that loud blast from a 650cc scooter, I also have them on two Goldwings
And they Really will not expect that loud blasting set of horns from a little IQ buggy