Hello David, copy-pasting the response I gave you in the other thread (sorry, I thought I was responding on this thread already and answering here is much more appropriate).
It's not clear to me what you're trying to achieve, if you just need to remove persistence cookie and always rely on pool LB selection method, there is "persist none" iRule instruction.
If you need to remove all cookies (why?) you can use my iRule, keep in mind this will delete persistence cookie as well. If you need to keep persist cookie, you can set it manually in the iRule with " persist cookie insert my_cookie_name "0d 00:00:00" " instruction and/or write some additional lines to save it & restore it after "cleanup cycle" is performed.