Yeah, you hit a vein - looking at the compounds there seems to be no tren in it.
When it comes to tren cough you don't even need to hit a vein to get it. Your muscles contain super small veins where the test oil is usually absorbed as a kind of depot.
Tren is super strong itself and it has something in it which makes it so that even extremely small amount of it will make you cough like shit. Tren can also cause kind of chronic cough which lasts for the cycle.
My language barrier makes it hard for me to write this, I'd like to explain more. This is pretty standard information, but I hope it helps.