I don't believe they doubled the Border Patrol. They have increased it but only incrementally. Congress appropriated the funds, but the Executive Branch didn't spend all of the money, IIRC.
I was close. There were about 8000 agents in 2001. The total number has doubled in the last 10 years, and is 6 times greater than when the last amnesty was passed in the Reagan years. Still hasn't done much to stem the tide/