Sorry, Richard. I know you thought you had a pretty decent plea: a low term of 16 months for selling cocaine. Not bad given your prior five prison terms. So you took it.
Little did you know that the feds were also investigating you (and other members of your gang). And would indict you all on RICO charges a little bit later. An indictment that included your state guilty plea.
A bummer, to be sure. But not a basis for you to withdraw your plea.
You got what you bargained for. It was less exciting once the United States indicted you, to be sure. But that's not the state's fault. That's a "your problem" rather than "our problem".