You can hear Pynchon pronounce it himself in his Simpsons cameo. :)
However. Assuming (rather safely) that he pronounces his own name correctly, NYT transcribed it badly. He doesn't stress the second syllable, as in "Lebron". He stresses the two syllables equally. That is, he says it as "pinch on", the way you might say it in "something to pinch on".
that was my intro to pynchon, being thrown head-first into the deep end. i did actually read the book, but it was... challenging. i appreciate the experience in hindsight, but rued every minute of it at the time.