390 fe, hei dist with msd 6a, comp cams CCA-CL33-224-3, 2105 edel intake, holley 670 street avenger, fmx transmission. It was running fine, has been for a while. I noticed this weird noise that happens under hard acceleration, it came out of nowhere. It sounds like a whoosh of air and happens in a couple inconsistent pulses and doesnt stop till I start to cruise. It only comes in in first gear, or only after 2,000 rpm, it literally sounds like compressed air, and when it happens I can feel a slight loss in the pedal. I've checked what I can, all fluids, no more leaks than usual, the belts are tight, this and that. I can rev it in Idle and nothing will happen, revs fine, and it starts up and cruises just fine too. I figure its an engine sound, I can hear it coming from in front of me, possibly from the tranny. I've never heard this from an engine before, and my 390 was tuned great and running like a dream prior, besides being slow and pretty bad mpg. Any input is appreciated, thanks.