I've been thinking this for a while now, does it sounds like an engine? is it tremolo + dist + pitch??
From what I've gathered, from trial and error, he used a flanger. I can't remember the tempo of the intro, at the moment, but find out what it is or choose your own tempo, plug it into a metronome, with the time signature, etc dialed in accordingly, and then utilize the 'TAP' feature to set the effect's tempo. Dime was also going by 4's, accenting on the 4 note. Alternate pick the first 3 notes (up, down, up) normally, but put a more inflection/accent on that 4th note, which should be down-picked. That's just a general rule, accent notes are to be on the down-pick, but if you're an innovator and rebel of music theory, you can accent on the "up". I do it all the time, because I do what I want.
I hope this rant helped. It's as close as I've come, so far. Good luck.