You can.....if you want. How long they will last is another matter.
The reason it is not recommended is because unlike copper plugs, iridiums are just iridium coated, not solid. So when you go to regap them you take some of the coating of iridium off, greatly reducing their performance and life.
I run 1.1mm iridiums in my gtst and they haven't missed a beat. It is lighty modified, 12psi, fmic, pod, exhaust blah blah usual stuff.
So either give them a go and see if they work, or go back and exchange them for .8mm factory gapped iridiums, or go with the rest of the crowd and buy coppers and gap them to your hearts content. Keep in mind coppers need replacing more often but are dirt cheap and will perform just as good or better than iridiums.
But for myself I have iridiums and haven't had a problem with them yet.