I get tren cough from all esters of tren, and I always aspirate. It can happen when a vein is just nicked, it doesnt have to be a straight IV slam.
Ill take it a step further, ever get insane burning in your nose and lips, and fingertips from tren that made it to the bloodstream? Thats how I know a BAD coughing spell (aka ab workout) is on its way.