I'm guessing that 190 degrees is the target vessel temperature then? The way I was reading it was that you were shooting for an internal meat temperature of 190 since you were already over 170 on the meat. Pork is usually well-done at 170 and a further increase in temperature (and or time) tends to shorten the muscle fibers which begins to dry out the meat and make it tougher, rather than more tender.

Knowing that it was a high collagen cut helps, since you're relying on the succulence of the gelatinized collagen (160-180 degrees) to cover up for the effect of dried out meat which begins happening above 140. A good way to protect against the drying out factor above 140 is to brine the meat prior to cooking.

I'll have to go back to Harold McGee to see what temperature he recommends for slow roasting pig, but I can't imagine that he would go over 180 on internal meat temperature.

Hope it was good!