Headlights Flickering

Hello there,

I have got myself the LS model.I bought it five months ago at around 108,000 miles.

A few days ago my headlights and a few interior lights including the clock, the shifter lights, check engine light (only comes back with an O2 sensor so have not replaced yet) and the TCL off light (which is always on and has been on since I bought the car) all started flickering.

They do not flicker when idling but do flicker when I give it gas, even in park if I rev it a little bit they will begin to flicker.

Last month I replaced the battery and alternator. Today I replaced one of the battery post leads because I noticed it was a bit loose, I was hoping that was the cause of the flickering lights but nothing changed. I then took it to O'Reilly's and had them check the battery/alternator/starter and everything came back good. They also had no ideas as to what the cause could be (did not really expect them to, just wanted to get the electrical checked).

Does anyone have any suggestions as to what the cause of my flickering lights could be?

Also, if there is anything I forgot to include that would need to be known, just ask and I will answer as best I can.

Thanks.