[Gelbster]

Some of us are Durametric fan boys(me) .The part that is often missed (also by me) is the knowledge and experience required to get a full, accurate diagnosis from the Durametric data. And then how to combine it with other diagnostic techniques/tools like an Electronic Engine Ear.
If you post the codes/freeze frame and other symptoms here with your problem described , you will be impressed by the upgrade in responses.
Buying the cable is a reasonable expense imho. Acquiring the knowledge and skills is daunting. Durametric Tech help is good but only in terms of how to use their tool(not clones from Flebay!). Understandably ,they are not in the Tech advice biz.
I use mine more than I expected.I have it loaded on an old lap top with all my other P-car sources/manuals.Invaluable.
Even if you use a competent,honest Indie(yes I am biased) , your Durametric info will get you valuable results there too.
I understand your 'crazy' comment -I have never experienced a more troublesome car - and we work on Jags, Rovers & AM !