The definition of a "split infinitive" is the insertion of an adverb within a compound verb construction. Therefore, "been funding" is the verb, and "secretly" is the adverb modifier that should live outside it.
That said, grammar is a tool with which we build. Raymond Chandler once wrote to an editor, "By the way, would you convey my compliments to the purist who reads your proofs and tell him or her that I write in a sort of broken-down patois which is something like the way a Swiss waiter talks, and that when I split an infinitive, God damn it, I split it so it will stay split, and when I interrupt the velvety smoothness of my more or less literate syntax with a few sudden words of barroom vernacular, this is done with the eyes wide open and the mind relaxed but attentive. The method may not be perfect, but it is all I have."
You're making music. Play the notes the way that the emotion feels strongest.
