I have acid reflux, treated with ppi, but sour/mettalic taste in mouth/throat and stomach gas discomfort persists regardless of avoiding triggers, sleeping on an incline, waiting at least 3 hours before lying down after meals?

In addition to medication avoid spicy and oily foods,aspirin, anti-inflammatory meds like ibuprofen or naproxen. Also avoid alcohol,nicotine,excess caffeine. Try coating the esophagus by taking a liquid combination of antacid&antigas,recommended by your pharmacist, 1/2 after meals and at bedtime. Are you taking the maximum dose of the ppi? Is a gastroenterologist involved in your care?

While you should loop your doctor in now to be sure there isn’t a health condition present that requires a different strategy, other non-drug approaches include avoiding late meals (within 2 hours of bedtime) and wearing loose clothing. If applicable, stopping smoking and losing weight (if overweight) may also help improve acid reflux.