In the episode, “Hermanos” (S4 E8), we see the cartel leader, Don Eladio, spare Gus’ life because, “I know who you are”. “But understand,” he warns “You are not in Chile anymore.”
In the episode, “One Minute” (S3 E7), we hear cartel captain, Hector Salamanca, say, “I don’t care who he knows.” The implication being that he is being asked his opinion of the cartel doing business with Gus. He votes no. The other members of the leadership want to go forward because of who Gus knows. Ultimately, Hector is overruled. The cartel & Gus Fring establish a business relationship.
In the episode, “I See You” (S3 E8), we see the Mexican police raid the home of Juan Bolsa, another cartel member, while he is one the phone with Mr. Fring. The implication here is that Mr. Fring somehow arranged the raid.
In the episode, “Bug” (S4 E9), we see cartel hitman, Gaff, sniping at members of Fring’s organization. Gus walks straight out to him, out in the open, essentially daring Gaff to shoot him. To do that, you’d have to being either crazy or very certain that you’re not going to get shot. This, again, underscores how important Gus is to the cartel. He is untouchable, even in open defiance.
The fact that this hidden past was not more fully developed is my only major disappointment with the series. I think that there must have been a decision to spend more time on Walt & Jesse’s family issues - that Gus’ storyline took the series away from it’s main path. But, there is so much hinting around that it’s a shame that it never went anywhere.
My guess is that Gus was connected to Special Agent in Charge Ramey. SAC Ramey was the head of the southwestern US DEA. In other words, a person perfectly positioned to protect Gus’ empire. He would be someone that Gus could call to arrange a raid in Mexico. This would also be an alternate reason why Hank’s bosses always tried to move him away from the Fring investigation. This relationship, if true, would’ve been a powerful, unspoken, element in the balance of power between Gus & the cartel.
But, hey, maybe I’m wrong. Would anyone else care to speculate about where Vince Gilligan intended to take us in Mr. Fring’s past?