I didn't answer over on the other board because I can't hear the sound for myself. Everyone's going off in all kinds of directions about it, but I bet they can't hear it either.

Sounds like intake noise, but are you sure you didn't change anything there? If it's intake noise it would be the same as before you changed your timing.

I bet if you get under the hood & open the throttle by hand, you can tell exactly where the sound is coming from. An open intake sounds like that, but I don't understand why it should change with timing. The factory intake muffles that sound with the air box & that funny resonator bottle hanging on the intake tube.