Had this discussion with a friend of mine years ago when I was a tren head and asfter some searching in my files ive found what we came up with
There are two systems the body use's for circulation, systematic and pulmonary. The pulmonary takes the deoxygenated blood back to the lungs for oxgenation, when we inject part of the injection will be taken up into the capillarys where it heads back to the heart out of the left atrium to the lungs and are expelled co2 and waste products in this case BA. Tren A dissassociates with BA far more easily than other hormones or ester's ie enan,hex. Inject slowly this will slow down the solution hitting the lungs instead of hitting it all in one lump, Always aspirate you could hit a vein and then the hormone and solvents (BA) will hit pulmonary circulation far far faster and you are likely to cough your head
I found injecting very slow solved the problem

and trust me I did use to get this a lot and to be honest when I switched to tren E it also helped alot which reinforces the above