I started using boinc near the start of last year but after about 6 months I just slowly forgot about it and it's been dormant on my HDD ever since. I have since moved distros twice (starting from Ubuntu then to Fedora then to Arch). When I stopped I was at the time also having issues with the boinc manager (Some of the text would be highlighted black making it extremely annoying to read and the page that shows you disk usage is behaving strangely, so I think it's a bug). I have wanted to try and get back into boinc recently and use my GPU for BOINC (which I would normally use for mining Zcash). Reinstalling with pacman doesn't seem to change much (even removing boinc using -Rsn). So I want to try and manually remove all of boincs configuration files so when I try and reinstall boinc sees it as a completely new install and asks me what projects I want to attach to. I also used grcpool for the last month that I used boinc and would like to stop using them, I know i'm not meant to ask here with issues with grcpool but if anybody happens to know where grcpool keeps all of it's files as well so I can remove it from my system that would be great. I can't remember much from when I installed boinc or started using gridcoin so I can't remember specifically where everything is located.

If you do a Google search of the forum, you'll find where BOINC stores its data. It's been noted on here before but I don't recall where offhand. I think it might be on the FAQs or Wiki of the site.

I'd have no idea about Gridcoin. Best to ask at their site or find somebody who seems knowledgeable about it, possibly on one of the projects listed in Gridcoin. Don't ask the project though. They have no part in it.

For Ubuntu:
http://boinc.berkeley.edu/wiki/Installing_BOINC_on_Ubuntu

More general Linux info:
http://boinc.berkeley.edu/wiki/Installing_BOINC#Installing_BOINC_as_a_package

I have 3 systems running Ubuntu 17.4 (as I recall) and use grcpool. There is nothing special about grcpool, it is just another account manager albeit not anywhere as good as BAM!, but it server it purpose.

For my systems apt-get purge boinc-client (or something like that) gets rid the client and the manager can be removed the same way. The account manager disappears along with the boinc code.

I have never used another distro so sorry, I know nothing about pacman, or arch but I recall Fedora has apt-get like Ubuntu. AFAICT boinc stuff is in \var\lib and in \etc directories named boinc-client

Make sure you detach from grcpool both on their web site and on your computer. If you stay on the gridcoin team and fail to detach you will contribute the the pool (thank you for the free gift).