OK, got to spend some more time on this problem... Blanked off the EGR valve thinking it might be leaking... no difference. Then, I disconnected the O2 sensor wire and BAM, the miss goes away. Now, this is a new Denso O2 sensor, which replaced a OEM unit thinking it was bad.. So, now I'm thinking the NWOR header just doesn't want to work well with this setup... RV cam, cylinders bored .020. Is it time for a LC engineering header???? Do they place the O2 sensor in a more ideal location? Any other thoughts as to why the O2 sensor disconnected would make the misfire vanish? (other than without the signal, the ECU richens up the mixture)...perhaps?