Wendell ("Mucho") Maas is Oedipa's husband… and he's not much of one at that. He used to work as a used car salesman, but was disgusted with his work and constantly complained about it to Oedipa. He later began working as a disk jockey at the local station KCUF—read that backwards—where his boss accuses him of creeptastically flirting with the young girls who call into his show. Oedipa knows about Mucho's sexual obsession with young girls (gross) and so doesn't feel much remorse when she begins her affair with Metzger.
Mucho is totally in the background for most of the book. When Oedipa receives a letter from him ("Potsmaster") that she believes came from Tristero, she wonders if even her husband is part of the conspiracy. Instead, we later learn that Mucho has been taking a ton of LSD given to him by Dr. Hilarius (5.202). By the time Oedipa reunites with him at the end of the book, she realizes that it is too late and her husband is lost… both because he's into underage girls and because he's hallucinating 24/7.
"Mucho Maas" closely corresponds to the Spanish for "much more." The phrase is pretty fitting, since Mucho hopes for so much more from life, and Oedipa in turn hopes for so much more from Mucho. Though Mucho is only the first in a long series of useless male characters that surround Oedipa, his thoughts on being a used car salesman do lead to one of the first truly awesome passages in the book.
Mucho reflects that all the trash left behind in used cars is "like a salad of despair," and he can never accept "the way each owner, each shadow, filed in only to exchange a dented, malfunctioning version of himself for another, just as futureless, automotive projection of somebody else's life" (1.12).
In the beginning of the book, Mucho's despair is kind of weird and anomalous, but by the end of the it's echoed in Oedipa's own reflections about Tristero and America. But, unlike Mucho, Oedipa doesn't give up hope.