Interesting bit of information....

[kwats]

My winter update on my '79SF was to find, refinish, and install a gas tank from a Standard, and while at it, toss those damn stock petcocks as far as I could throw them. Did all that, I installed some ball valve petcocks, and refinished the inside of the tank with POR15. I am impressed with the quality of that product. While at it, I replaced all the fuel lines with current lines that are unaffected by ethanol, and completely cleaned the carbs.
I also installed some lowers that I matched the paint on.
What I find interesting is that after all that, my mileage has increased by 3 mpg on average. I didn't expect that. For the last 3 years, I have consistently gotten 39-40 mpg. First 4 tanks this season have gotten 43 mpg average....

[motoman]

My winter update on my '79SF was to find, refinish, and install a gas tank from a Standard, and while at it, toss those damn stock petcocks as far as I could throw them. Did all that, I installed some ball valve petcocks, and refinished the inside of the tank with POR15. I am impressed with the quality of that product. While at it, I replaced all the fuel lines with current lines that are unaffected by ethanol, and completely cleaned the carbs.
I also installed some lowers that I matched the paint on.
What I find interesting is that after all that, my mileage has increased by 3 mpg on average. I didn't expect that. For the last 3 years, I have consistently gotten 39-40 mpg. First 4 tanks this season have gotten 43 mpg average....

Actually, the lowers mounted on fairing WILL increase mileage approx. 2mpg. Tested that scenario a few times on my Venturer over the years....

[BA80]

I also installed some lowers that I matched the paint on.
What I find interesting is that after all that, my mileage has increased by 3 mpg on average. I didn't expect that. For the last 3 years, I have consistently gotten 39-40 mpg. First 4 tanks this season have gotten 43 mpg average....

The lowers may increase mileage but as you said you cleaned the carbs too. Be sure which was the cause for the effect.

One thing I noticed about running lowers is if your riding in a fair crosswind it makes the bike feel like it's going to get blown out from under you. Kinda spooky at times.