Analyzing data logs

[Hella Basa]

https://datazap.me/u/hellabasa/oft-stage-2?log=0&data=1

I'm still learning about tuning so I've been doing a lot of reading. I mostly followed this guide http://www.ft86club.com/forums/showthread.php?p=1842501
I just have a couple of questions.

1. Is there a way to tell if I have an exhaust leak by just looking at the data log?

2. I noticed that sometimes my AFR would jump to 20, is that something to worry about?

If anyone could take a look at my data log and tell me if there's something I need to worry about. Thank you all!

EDIT:
mods - OFH2 and muffler delete. stock everything else
tune - OFT stage 2 uel v2 tune(still testing v2 and v4 to see which one runs the best for my car)

[tomm.brz]

afr goes to 20 when off throttle since it cuts fuel, normal
if you have v4 tune and didnt touch fueling or maf scaling you dont have a leak, at least not near the sensors since your fuel trims look good
you need to log also flkc to see if it knocks

[Hella Basa]

Originally Posted by tomm.brz

afr goes to 20 when off throttle since it cuts fuel, normal
if you have v4 tune and didnt touch fueling or maf scaling you dont have a leak, at least not near the sensors since your fuel trims look good
you need to log also flkc to see if it knocks

sounds good. I'm using the v2 at the moment.

Will log the flkc today, thank you sir!