I heard that in town driving , stop and go traffic and low speed 25-35mph isn't good for the new engines with DEF tanks clogs up particulate filters and such really fast , I don't have a new one yet currently have a 97 12 valve just trying to find some info on the subject thanks for any input.

 

The def fluid doesn't really clog up during in city driving. But the dpf system is what to be carefull of during alot of in city driving.
If you are only doing city driving, and no freeway driving then the dpf filter will soot up alot faster because the dpf system can't get hot enough to do a proper burn, or (regen).
Then after a while the dpf will want to do a regen, so you will need to get to a freeway and drive for a while so it can do a regen.
Yup alot to think of.
I have a 97cummins also.