Thanks for all the info everyone!
Yea spaghetti arms stretch Armstrong.so found the thread where the guy claims to have installed the downpipe without cowl removal and was able to do it in 45 mins. it was on 9th civic dot com /forum/threads/how-to-install-a-rv6-2012-civic-si-bellmouth-downpipe.5727/
I really don't know. I'm sorry. I just know he was NOT open to the idea of taking the cowl off lol. He didn't mention any frustration with the O2 sensor, just some frustration getting to the top bolts until he found the right tool to use. Wound up taking him 45 mins to an hour total.Maybe I will give it a shot when mine comes in then. Did he leave the O2 on until he removed the DP or did he remove the sensor with the DP still installed?