Gen iii - Accelerator Pedal Issue - Response is worse

I bought my ride in 2017 and it’s 2014 Model with 70,000km ODO. After driving few months, I figured the pedal response is getting way smoother and it’s not acting a little bit pushy on ECO mode. No warning Sign, Nothing But the huge impact on Bad Fuel Economy. It’s dropped from 22 km/L to 18 km/L. I swapped a pedal accelerator part and everything’s normal.
but after 3 days, the new pedal acts the same. I remember last time i figured the same issue when i refuelled High Octane full tank and now it’s the same scenario.
Any technician / expert would mind helping me in that? Im worried now.
i attached the replaced pedal part as well

 

Well im a newbie but i can assure you it’s the pedal issue, nothing else. It’s not an uneducated guess