Question about fuel economy 4"vs. 5"

I was wondering if anyone on here could comment on the difference in fuel economy between the 4" delete exhaust vs. 5"?

Has anone on here gone from 4" to 5" and actually tracked mileage in both configurations?

I have 4" and have tracked my mileage religously for 5 years. I do great. Better than my buddy who has 5" exhaus and ran the same rim, tire lift and tune combination as me.

I get between 21-23mpg hand caluculated consistently but want to go to 5" for better sound and home my mileage will increase as well.

My concern is that my budies identical truck in that configuration was worse and the only difference is our exhaust size.

Can anyone else confirm or deny if my mileage will improve or drop based on their experience?

Thanks