Why are ISIS militants driving Texas-made Toyota trucks apparently modified for U.S. Special Forces?
Pictured above is a literal parade of Humvees captured by ISIL forces from abandoned Iraqi Army positions. During the pull-out in 2011, it was deemed that bringing home all of our equipment would be a logistical nightmare and horribly expensive. For that reason, massive amounts of aging and used equipment was given to the Iraqi at discounted rates.
Skip to Summer 2014 and we see that many assets, particularly those housed in Al Anbar and Nineveh provinces were taken after Iraqi forces fled and abandoned them. This list of American assets acquired this way includes uparmored Humvees, utility trucks like the Toyotas, weapons including small arms and even artillery.
As for the Toyotas, those aren't special forces vehicles. They are utility vehicles that US military bought, with some special modifications to survive in the desert environment, for our non-tactical support needs. When I was in Iraq, we used them in secured locations for our basic mobility needs while on base. They are much cheaper to use and easier to drive than a Humvee, so if four of us needed to go to the post or to our living quarters, it made much more sense to take the truck than the Humvee. They do have special aftermarket modifications because they are being used in a grueling desert environment.
After we used them, we gave them to our incompetent buddies, who lost them. End of story. The article you pointed out is using some true points, such as the presence of American equipment and American past involvement in making them and getting them to Iraq, but has obviously put on massive common sense blinders in research that explain their current existence. The sources, instead, uses them to point to the same ridiculous meme of, "The American government are behind it all!" as has been done since every bad geopolitical situation since the Iran-Hostage Crisis. It is also the type of mentality behind people who are 9/11 deniers, which your source, just so happens to be:
Please vet your sources because it is easy to find information. Information is everywhere in the modern age, but the conclusions they lead to can be horrifically wrong if you aren't dealing with rational people.