Download Speed Issues - Peaks and Valleys

[Jimmy-BewareOfPie]

Okay, so I'm having a major DL speed issue here when it comes to X-Com 2 and it's beginning to deeply annoy me.

I have already done all of the following:
Changed my download server (I have tried servers in 10 different countries across 10 different time zones, and every server on my side of the U.S East Coast including the Canadian ones and several in California)
Disabled Avast Antivirus
Disabled all other background programs
Power-cycled my modem (I am wired up, not wireless, most days)
Reset my computer
Flushed my DNS
Flushed my Cache
Disabled my firewall
Reset my computer *again*
Run my connection through a router
Run my connection through wireless
Reset my modem
Changed my network cables.

What happens is simple - The download speed will build up to my maximum (5MBs - 600kbs) It will sit there for between three and eight seconds, and then the connection will bomb down to around 150-100kbs and then slowly inch back up, over the course of about a 30-45 seconds, to about 300kbs. It fluctuates there for around 10 or 20 seconds before charging up to 600kbs again, then the process repeats itself.

It does this for Every. Single. Server. That. I. Have. Tried.

I can pull reliable and consistent 600kbs speeds on nearly any other downloading platform I have. I have ran a speed test confirming my speeds are accurate to the Detroit node where my original download center was set.

I have been running this download for five hours consistantly before I tried to fix the problem. I have downloaded 5 GB of the game, which amounts to an average download speed of 270kb, which is less than HALF of my actual speed. As far as I know, I am not being throttled by my ISP.

Please help.