^^^^ +1 what Hank said above.
First off, look to the ribs themselves. Were they enhanced? Most you buy out there are, in some type of brine or another. I would highly suggest finding un-enhanced ribs.
Then, the 220 was largely a waste of time and you definitely had not gotten to the portion where the fat renders. Combine that with a cook temp of 350 where you've basically fried/seared the fat in it. FYI: spares are significantly more fatty than baby backs...
Also, like said above, when we talk cooking temperature, we're talking about the temperature ON THE SURFACE, not measured by one of the various external mounted thermometers, etc.
Try cooking in that 250-280 range next time, the whole time. On my smoker I cook BB's religiously (will cook 14 racks on Saturday), 270 degrees, I foil at the 1.5 hour mark, they're DONE DONE DONE just before or right at the 4 hour mark.
It sounds to me like yours werent done yet, and the two temperature shifts that you used insured that you had the most fatty meat possible...
Hance - Lake Dogs Cooking Team - MiM/MBN/GBA CBJ and comp cook
Lake Sinclair, GA (strategically about an hour from darn near anywhere)
Started competing in chili cookoffs back in the 1990's and have competed in more than I care to count. I became a CBJ in MiM in 2005, then MBN and in GBA in 2010. I've probably judged 130+- BBQ comps (sanctioned and unsanctioned) over this time. That said, I really enjoy competing more than I enjoy judging, and hope to get back to doing 4 or 5 a year in the near future.