I work in the eCommerce industry and I deal with this stuff all the time.
Let me shine a light on this situation, and again, I have no affiliations or ties to BMS.
He's selling a product that isn't DOT approved or road legal as it lets you get passed a specific code that BMW wrote into the DME/ECU to protect average road going cars against emission violations. It is designed for that situation where your car isn't registered for road use, therefore not required to adhere to the laws of public motorways. The government could fine the bejeesus out of his company if he doesn't word himself correctly, also he could also be sued by an individual who uses the product and sees legal issues for using the product on public highways. That's the explanation for the short vague answers.
As for the rudeness, that's misplaced. Something was lost in translation with this message. You feel the fact that he turned you away for business and didn't elaborate on what his product could do for you was a blatant jab at you. Wrong. He was just protecting his ass. I've had one or two interactions with Terry's company, one of which was to Terry directly. I asked him a series of questions in regards to his JB4 ISO piggy backs, he answer maybe 2 out of the 10 questions I asked. I told him about the Dinan stg 2 tune that was on my car, and his major reply was it would be much faster with the JB4 stacked on top. I thought about it instantly in the same manner. "Doesn't this man know who I am?" No he doesn't. It doesn't matter how many racecars or bikes I've built, I'm not anybody that's spent money just yet with him nor does he realize any of this. If he woulda told you that you weren't smart enough to read and research the forums, yeah that would have been rude as hell and I would have sent him a package with dog shit in it.
Keep in mind, this man most likely answers over 100 emails a day. I know I approach twice that sometimes and I can be short/to the point. Don't take it personal and remember, he's not selling you a house or a set of tits; it's just a car part.
He was correct in saying my car is a lot faster with the JB4 g5 ISO piggied on the Dinan flash. I didn't buy it directly from BMS, which I kinda regret but I did get it on a smokin' deal. I don't expect him to troubleshoot anything for me but I know if I get on n54tech, he will shoot an answer out if he can.
Have patience my friend, the internet is a crazy place.
2007 335i Sedan
1991 Toyota Supra, 1JZ swap, T66 single, supporting mods.