backfire, 1-2 upshift

["David and Debbie Steele" <cvo24@chicagonet.net>]

 Gennulmen, (and ladies)

  The scene: '98 JettaGLX, 19k miles, Garrett v.10, K&N, mod airbox, premium
  fuel.

  Occasionally, and only on the 1-2 upshift, I'm getting a backfire into the
  airbox (or so it sounds) as I engage the clutch and give it power. I
 thought
  that it was perhaps a temperature related thing (engine not up to temp) or
a
  fuel related problem (was running CITGO premium, but switched to Amoco
  premium); alas, it did it again yesterday, engine temp good, oil at 206
  deg., Amoco in the tank. I had asked Todd for his ideas, and he suggested
  that I change fuel (before I had) but the pop goes on. Any ideas? Is it
  maybe the reformulated fuel that the VR6 just doesn't like? I'm starting
to
  get  a little worried about this.....

  Dave
  as above
  pop-goes-the-weasel edition