For my manometry I was not allowed to eat several hours before, so that the stomach would be empty during the measurement of the LES-pressure. I guess otherwise you risk throwing up, when they put the small tube in your stomach.
During the subsequent 24h impedance / ph-test I was told to eat my typical trigger food, in order to provoke reflux, so that the could really see what was going on in my esophagus in the worst moments.
Side note: In spite of all that, my results showed only small amounts of reflux, although I'm more than convinced to have LPR. I think it was due to the fact that all the testing was stressful for me and whenever I'm really stressed I don't have any symptoms because my stomach motility is enhanced. Also maybe it takes longer for the food to provoke reflux. That's why I think, if I will ever do these tests again, I will eat trigger food already the day before, so that there will maybe be some more reflux on the next day. It's just a thought, however.
I'm crossing my fingers for you, that they can track down something and then help you!
Thank you ^^ Some people have mentionned starting bad foods 4-7 days before; that's scary, especially since I'm already at a point where I can barely swallow water!