Renault — Unresponsive and unstable Duster 85PS diesel. Bad support received from ASM and senior management on the concerns raised.

I own a 2019 Duster 85 PS diesel vehicle. I have raised concern on lower pick up and mileage. Before coming to Renault i was getting 15km/l and after 3 months its the same after visiting the service center for 16 times. Local dealer was supportive and replace few parts but actual issue is Once i got with test turbo or when i got the vehicle serviced or when team cleaned the EGR value or with new intercooler or after replacing the new turbo, i could feel the pick up/power and it takes ride without much throttle but as time goes i feel the power lag and to reach 90km speed i have to peddle more and which will increase the RPM and consuming high fuel. I have shared other duster vehicle statistics and its happening only in my car.
Renault expert drivers took the test drives in 3 cycles,
1. With AC, maintaining 70-80 km speed for 33 km stretch and got 19.7 km/l.
2. Without AC, maintaining 70-80 km speed same 33 km stretch and got 22.5 km/l.
3. With AC, maintaining 90-100km speed for same 33km stretch and got 15.1 km/l.
I asked to increase the throttle and to drive in 90-100 km speed, where even the road doesn’t support constant high speed but just to try and touch 100 km speed at some point, after covering the 33km stretch we got 15.1 km/l, almost lag of 5km/l when you just increase the speed to 90km or 100 km. Is this expected and is this the actual stability of 85 ps diesel duster?.
Ideally drop of 1 or 2 km/l is accepted right not 5km/l.
Even Renault team denying to share the 3rd point above in their resolution email, this is what my actual issue is.
I have driven 8-9 duster same model vehicles and myself nor the existing buyers faced this kind of issues. Whether the duster is designed to ride in 70-80 kms speed to get mileage and proportionate drop is expected if its speed is raised not 5 to 6 km/l.
Renault team is not responding to my emails. I would suggest the readers/public to please stay away from Renault products, i could share the kind of responses i received from CRM or ASM.