What bad340 said.... I work on them and am currently looking for a 13-15 3500 single wheel long bed crew cab. 90% of the "delete" stuff you hear is related to the late 07-12 6.7 trucks. If you're looking at something in that era, and don't emission test, delete would be the FIRST thing I'd do. Hindsight being what it is, the DEF equipped trucks (13 up) have had little to no issues. They do indeed "tolerate" light duty driving a lot better, get better mpg, extended oil change life, and have two fuel filters which is something they've probably needed since 03 when the common rail came out. One thing though.... they like tires. You'll be lucky to get 30K out of a set... most get changed at 20-25K.