gmc electric fans

[ontime1s]

I have a sierra Z-71 w/ the 5.3 flex fuel(2006).I used the Predator(U7192) to put in the 87 tune.All is working well but I noticed my dual electric fans, by the radiator,working much harder to the point I can hear the humming in my cab,but only after I fuel up.It lasts aprox 1-1.5 min. then it goes back to normal.The fans are working all the time and seem ok,until I once again stop refuel and 5-10 sec. after I crank up I begin to hear the fans working loud 1min later they quiet down to normal operation.It won't do it any other time,even if I take the gas cap off for a bit or let it idle to get truck nice and hot.I have to put gas in it to have it happen.Is this bad???

[mikel]

This is fine.

Thanks