Suddenly ALL HTTPS Sites take 12-30 Seconds to load (All Browsers Except Firefox)

Question

THE PROBLEM: Starting about 4 days ago, ALL https:// sites now take 12-30 seconds to load ONLY on my machine, except on FireFox 49.0.2, which seems to perform mostly normal (in terms of speed). No errors -- just SLOW. Chrome, IE, Opera browsers start to a blank page at normal speed, but going to a https:// site takes "forever". All browsers perform normally and speedily when rendering a standard http:// page.

*THE STORY: Monkeying with Self-Signed Certificates and Firewalls? So -- to be clear upfront, I am assuming that this is ALL my fault. That said, I really, REALLY need your help. I am a developer and I was trying to change IIS Express to allow development in SSL mode. I read carefully (I thought) many articles from some very smart people (names redacted to protect the innocent) and made some headway but ultimately gave up in the interest of time. A few Self-Signed Certificates were created in the process and the firewall was modified via a few "netsh" commands. I restore most everything (as far as I knew) back to the way it was but I am guessing that I missed something. The problem now, certainly an unintended consequence, is that it takes inordinate amounts of time to search (as Google uses port 443 for most everything). It's the kind of problem that would make me migrate to a new system to get rid of this problem (my equivalent of getting a few root canals without Novocain).

I searched and searched and am desperate. Please help! :-( Thank you!

HERE'S WHAT I KNOW:

1. It's NOT my internet connection. I am looking at a modest 12Mbps/6Mbps connection. Other machines on the same network perform normally to the internet. Again - everything works normally over port 80 (http:// traffic) on my machine.
2. It's NOT a bloated browser with plugins. I've stripped plugins and still get the same bad results. I've started by command line also (e.g. iexplore.exe -extoff) and still the same problem.
3. I momentarily turned off the firewall to test and it still yielded the same lousy performance on https://.
4. Temporarily disabled MalwareBytes. No change.
5. Except Firefox, all browsers are affected. Why does Firefox seem to work well?
6. No proxy server.
7. Good google ping times (time=69ms TTL=51)
8. Once on Google, staying WITHIN the google site performance is great (as in normal).
9. Google suggestions (ajax) work immediately in the searchbar (although they use port 80)

MY HARDWARE: Windows 8.1 Pro i7-4770R CPU @ 3.2GHz / 16GB Ram Samsung SSD

Answer 1

So - as I eluded to in my OP -- it was all my fault. I know better than to monkey with things that I don't understand, but if we all followed that to a tee there would be no progress.

The problem was that there were two certificates - a localhost cert in Trusted Root Certification Authorities and another localhost cert and BOTH had a Cross-Certificate Url added. Presumably, browser searches on my machine would time out trying to locate the url, hence the 9+ second stall. All works well now and I can suppress thoughts of migrating to a new machine to rid myself of these problems for another time. ;-)

Thanks for the help @Ramhound.