I think EGR valves have a worse reputation than warranted, maybe early ones from another manufacturer gave them some notoriety. It seems you have ruled out the valve as the cause of your symptoms, I would also rule out fuel filter as that is usually trouble free and would not manifest itself at a particular rpm, the car has a pumped high pressure fuel circuit so varying engine demands do not cause fuel starvation.
It may be best to put the EGR valve back to operating conditions to keep the engine management happy. With a low mileage car driven sedately, it may also pay to stretch it's legs once in a while - this will ensure all operating parts get exercised over their full range of movement and high temps are quite effective at cleaning up an engine. Just holding a lower ratio once a month is enough.
Plugs should have been changed on this car at some point, if not sure then that should probably be done; closely related to this are the coil packs, some have experienced issues with these - removing and visual inspection should yield clues.
Lastly some cars with an electronic throttle have developed a wiring fault, that manifests itself as lack of response between the pedal and the throttle body. Your car is later than the majority of cars that have exhibited this fault so I fell it is less likely but nether the less as it is a temporary break in a wire the conditions that cause it are often repeatable and similar.
Most of these faults will cause a temporary fault code to be logged, although it will not illuminate the check engine light. If you can have this read or use an OBDII code reader yourself then it may be easier to resolve this.
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TG