Long story short, traced an issue down to my left carb having a very slow float leak and I have a few questions.

Seat was removed... very tight, had to pry it up. O-ring looks too big and smushed (out of round). I assume this is abnormal, but just wanted to double check.

Also, should a close visual inspection be good for the needle/seat, or is it one of those things you can't just tell by looking at?

You can usually tell when it's shot or not right. From the sounds of it, the wrong o-ring is in there. The correct one will just, feel right. It won't bunch up, or look crushed.

I figured as much, thanks.