Hey there Joel, since no replies to your question about residual nutrients or foods and the PEG has not been answered yet, I'll share with you what I have learned.
Before a feeding, you can simply insert an open bolous or (syringe) into the peg tube. Then hold the syringe at or below your stomach level until some of the fluids in your stomach start to fill the syringe. If the color of the fluid is the same as the formula, or is actually the last foods you have eaten, then you are not digesting the foods. This is residual foods and is not a good sign and should be treated by your doctor. If the fluid is clear and water like, you should be fine. After the length of your last post on this subject, I would assume you have already gotten your answer. If not then here ya go.
Good luck and I sure hope all is well.
Brentt