It's honestly a crap shoot! But, if you can financially recover for a bad failure and you feel like it's a nice buy, then do it. They are nice smooth rides.
You need to pull it at the same time as tuning.. that's the whole point.. as it's usually stopped up or will be very soon.. especially if it's NOT regenerating.
It's a good idea... my truck had the worst timing.. it seem like after an hour drive I would park and home and as soon as I'm fixing to park you could tell regen just kicked in.