I found this installation manual for this option.
Frankly, I spent a number if years working on analog noise blankers for weak signal receivers I designed and the first thing you need to know is that noise blankers have to be early in an IF system where the bandwidth is wide. Mine were at 10.7mHz prior to crystal filters.
The more selective the IF, the more that impulse noise is stretched and the more difficult it becomes to blank it by turning off the noise gate stage.
It is possible that this circuit did a little on automobile impulse noise that was not energy dense, but by placing it at 455kHz, they assured that the impulse noise was wider than if it had been right after the firs mixer at a higher IF frequency (3035kHz). Unfortunately, that IF is not used on 160 and 80 meters.
Here is the manual and good luck getting it to work. 73, Mike
http://ww.w.hammarlund.info/info/accessories/immunizer/immunizer_install_11pg.pdf