It's real stuff
Bro -
If he got the taste, sort of metallic at the back of his throat soon after the inject then his fina is good. The taste is one of the ways to tell you are injecting the good stuff.
In regards to the cough, it sounds like he probably did hit a vein.
Tell him to asperate the next time.
Is he okay now, if so then maybe he only shot through a vein and got some of the fina but not all of it in the vein.
Later bro,
LT