4 days post op. Taking a plate out of the microwave, my right upper breast made a farting noise.

The sound you heard is because air entered your breast implant pocket when the skin was open during the augmentation surgery.  This air mixes with with fluids placed in the breast implant pocket.  The air and fluid mixture in a closed space creates an audible sound.This type of sound usually disappears after the first week post op.  In my experience, this is both quite common and nothing to worry about.  That being said, make sure you report this experience to your personal plastic surgeon. 

Greetings. This issue is very common and it is usually due to the breast implant rubbing up against the pectoralis muscle. This can also occur when there's a small amount of air trapped in the pocket. The air will go away as time passes and the sounds will also go away as the capsule around your breast implant begins to form. In the meantime, don't eat any more beans and if the sounds are very loud blame it on your husband! Best wishes always, Dr. Aldo