Tren cough is more common with Tren Ace than Tren E. What causes you to cough is when some of the tren gets into your bloodstream when you are pinning. Unfortunately even when you aspirate, it may not draw blood into the syringe but that doesnt mean that there isnt a small blood vessel in the area that is pierced and then some of the tren can get into your bloodstream.
Trust me - you will "know" that you have it because you will have an almost immediate uncontrollable cough. For me it generally only lasts for 30 - 60 seconds. So it is only a temporary thing.