Last time I went after improvised components was when Borann was the hot mining system. All the people getting ganked there pushed the controlling faction's security rating into the red, and there were tons of HGEs to be found - I actually wonder if traffic is a better indicator for HGE spawn rates than population these days? Either way, I went there, said "forget diamonds, this is the real jackpot" and completely filled my boots.
I also found civil unrest pretty regularly in Diaguandri when I was there and that got a decent amount of spawns. Likewise, Deciat.
So the best places to farm improvised components, from my purely anecdotal observations, appear to be high-traffic systems with a lot of negative security transactions and relatively few people that actually make their home in the system running missions to counter the negative effects. So... ganking hotspots.