Well sorry to be anticlimactic but what I ended up doing was removing the Crazy Red Italian air horn and giving everything a very thorough cleaning. I think I am able to salvage the horn.

It doesn't work great when the car is off but my voltmeter indicates that while off and pressing the horn the voltage is around 11 or so. With the car on and pressing the horn the voltage is 14 ish. With the car on the horn works better than I have ever heard it in my life.

I should preface this by saying that we bought the car 9 years ago with the horn installed and it never worked great. It was ok. Now it works great when the car is on.

The only reason I went through the trouble is because odd enough it has some sentimental value as being the only upgrade the car had for many years and I could not come to grips to throw it away. I figured it was worth trying to fix and I think I have. I took apart both trumpets and sprayed both diaphragms with a pb blaster silicon spray and I sprayed the air compressor outlet with some of the same spray.