Remember that if you remove the egr valve you will always reduce soot production. If the ecu isn't recycling nox back into the combustion this will reduce soot.
Nox burns cooler than air and therefore produces an inefficient burn of the fuel leaving a higher quantity of soot.
The 335d egr implementation is quite relaxed compared to some Japanese diesels. So even with the egr active soot is not as aggressive as some cars. I've seen the egr valves in some Japanese cars absolutly caked in carbon in just 20,000 miles.