Car feels a little sluggish with a Full gas tank?

[TheAnswer_03]

Whenever the gas tank is about 60% to 100% full, the car feels a little bit un-eager to move - like I have to hit the gas pedal harder for acceleration. But whenever the fuel level is about 50% or lower, there is noticeably more pep when accelerating and I don't don't have to depress the gas pedal as hard to achieve the same acceleration. Is this just because of the difference in weight btw a full tank and half? It's only about a 50 pound difference isn't it? Would cleaning the fuel injectors or some other type of maintenance help?

Car is an '07 Mazda 3 Sedan 2.3L Auto.

[staax]

I've often felt that my 2012 2.0 feels a little sluggish after fill up too but I assumed it was all in my head.
I'm sure the extra weight wouldnt matter that much.

I've just been assuming its been bad gas... the prices are falling. Maybe the octane content is too!:chuckle