Since I got the car the gauge will only show up to 3/4 full and stay there for a while until the level drops below that then it shows the correct level.

I've read a couple people had the same issue when something got tangled in the tank after replacing a fuel pump, and I can tell the left side fuel pump has been replaced previously.
I took the caps off both sides of the tank, looked inside and kinda wiggled my hand around. I could see and feel a bunch of tubes/wires but I have no idea where the float is and didn't notice anything that looked tangled.

Filled it up hoping that maybe I got lucky and untangled it while I was poking around, but no such luck. Any tips on what I'm looking for, or what needs to be done?

 

See the clear connector with the red wire coming out of the top of the fuel pump? This connects to the level sensor (there's one on each side of the tank). Just follow that small harness, and you'll find it. It's pretty common for the float to get caught under wires or hoses after a fuel pump change.

 

Tanks, I'll give it another try after I burn off some gas.

 

Got the tank back down to almost empty today so I gave it another try.

My problem was on the driver's side (and it was obvious that pump had been replaced), one of the corrugated hoses that connects to the top part (filter I think) was hanging on the side towards the door, which is the side the float is on. I had to twist it into a loop for it to be out of the way/on the other side. Filled it up again, and it worked. Now my gauge finally shows 4/4 and it feels good (though it took almost $95 to get there).

 

Good to hear!