when tuning up my 91 integra (non- vetec motor) i advanced the timing to a point where the motor ran good, but i also had that strange sucking sound when i accelerated, not knowing if it was damaging i retarded the timing and everything went back to normal.

my first(stupid) thought was that the fuel air mixture was igniting while the intake valves where still open forcing air back out....but that is impossible because the motor would not be running at that kind of advance... it would take like 90 degrees of advance i think...

I am only writing so you know that you are not alone and are not crazy... i still dont know what that noise was.