1st year that Dodge (RAM) had a DPF was 2007 with the 6.7L Cummins (the 5.9L CTD didn't have DPF)
Run with exhaust break on, limit idle time which should be limited regardless) and drive highway speeds to clean it out it will be OK
Excessive idle, low towing speeds and it will soot up....
The long hauler didn't have a 2005 that he removed the DPF from. Sounds like he was 'blowing soot'. YOU even mentioned 2007 as first year.
And it is illegal to remove any emissions devices. Federal law makes it illegal for ANYONE to tamper with, disconnect, remove or otherwise render inoperative ANY emissions-related control device.