The 8000's have much more in common with the 7900's than they do with the 8100's. The engines, transmissions and engine cradles are identical and interchangeable. The DPF system on the 8000's is an add on passive system with its own computer module, harness and pressure sensor which are separate from the Cummins ECM. The system was a stop gap used only on these buses. It was very basic and does not have the capability to regenerate (clean the DPF) on its own like the active system found on the NG hybrids, 8100's and newer buses do. The DPF's must be changed out every year or they will plug the exhaust which in turn causes the pressure sensor module to send a signal to the main ECM to shut down the engine. While at Queensway I remember attending several road calls for a stalled bus where this was the case. Luckily for us techs all we had to do to get the bus going again was to pull the pressure sensor module fuse then the engine would restart. The filter was then replaced after we drove the bus back to the garage. On the newer buses once a code trips for a plugged DPF it usually ends up on a tow truck.