My return lines went quickly, too. And they keep going quickly.

I've lost four brass lines to this stuff.

Also, I've noticed a significant increase on average with black soot, and more often than before, suffer a major hit in fuel economy. For instance, I've been averaging 26 - 28 mpg in my 350SD, last tank yielded 22 mpg. More PM than a Semi can paste at full load. And, FWIW, my EGR spring is perfectly fine (claps right away after 10 psi is applied with Mityvac).