I would think that would not be unheard of if your EGR is not functioning. The EGR only functions at cruise/part throttle, and the timing is increased with the EGR for cleaner burn, thats it purpose. Remove the EGR, and some timing would probably need to be removed at cruise speeds.
Make sure the EGR is disabled in the chip first, then remove timing if needed. I can't remember if timing is added on top of the main spark settings only when the EGR is enabled, or if its already added into the mian spark table values.