I have been recently having an issue with my car where the power isn't what I remember and the fuel economy has dropped from 280 miles per tank to 200 miles per tank.

The radio LED occasionally flickers into just a line across or everything lit up in the morning. This also occurred last year before I replaced the battery terminals.

My ignition coils were replaced 30k miles ago and the spark plugs were replaced 10k miles ago.

What could be the issue? In addition, what are the part numbers to replace the battery cables?

 

Fuel mileage could be due to coils. 30k is about when you should think about changing them.

The display -- do all the radio controls still work, change stations, volume, etc?
If so, the connector behind the display could be loose. With all your footwell lights and PC connector, was the radio stack wiring tinkered with?

If you're worried about the battery, it's easy to test at your local AutoZone or with a multimeter at home.

 

The drop in fuel mileage dropped immediately after I did not drive the car for a few weeks. The radio LED flickering came back at the same time which occurred the before I replaced the battery terminals.
The radio does work and all the buttons have full functionality.
I do plan on changing the ignition coils soon.
I changed the battery last year which leads me to concern that the cables themselves may be going bad when considering the battery terminals went bad last year.