It's the fina and not the BA. Some people are just more sensetive to the drug as far as side effects go,just like some people experience sust flu and others have no problems or pain. I am prone to the "death cough" that fina can cause so I feel for you gymrat. If I hadden't been warned about it with a very presise discription of the "call 911" severity of it along time ago by Stickler, I would have thought I was dying the 1st time it happened to me. I average about every 3rd shot with some degree of cough.
I was running fina and prop a few cycles ago (not premixed together) and drew up the fina 1st,prop 2nd...I didn't finish out the prop that cycle and so was using it up later in a fina-free cycle. Well I swear I had a fina cough episode just from the small amount of residual fina that had cross contaminated the prop bottle from that earlier cycle. And if you have ever experienced it,along with that funny taste in the mouth...you know there is no mistaking a fina cough. That's why I don'y think dilution will do much good if you are that prone to it. Injecting very slowly(like 5-10 minutes per cc) and pausing everytime you begin to get that taste in your mouth is about the only sucessful way I've found to minimize fina cough. (and mine was human grade so filler was also not a possible issue).
Hope that helps ya bro.