My truck keeps randomly throwing code 335, EGR feedback signal is/was out of range. CEL will only stay on for like 20-30 seconds and it only comes on once every couple of weeks.

I replaced the DPFE probably a year ago, can't be more than 10k-15k miles on it. This all started when I had my truck straightpiped for a couple days. I don't see how a lack of backpressure could screw up the DPFE though.