Traditional uses of feverfew include fevers, inflammation, arthritis and migraine. I haven't heard of it being used for 'sour stomach' - acid reflux, indigestion, or the like. And an occasional side effect is mouth sores (ulcering). So I would consider something else. Marjoram is one herb that is well regarded for 'sour stomach'.

In addition feverfew may be of help in certain skin conditions (i.e. eczema and rosacea); on the other hand it can cause skin irritation in susceptible people. If the feverfew is growing near a cornfield, I'd be concerned about possible pesticide/herbicide drift and contamination - might be best to save seed and plant in another location.

Feverfew will lower your blood pressure ... and if you are a regular user of it, may make it impossible to get the BP back up. It can permanently damage the muscles in the artery walls. (that's why it works in vascular headaches like migraine)

If you have a "sour stomach", try peppermint or chamomile.