The J and H are very similar, but they say that the H is "more racing".
A friend of mine have one H in his S3 for more than a year, remaped with full exaust and some more thing's and it's running okay, without any kind of problems.
I think that i will buy one at Audi store and try.
That boost machine is interesting, i will see if i can find some more info about that too.
Any news from ABT?
Regards