When cruising on the highway, my scanmaster used to show the EGR quickly bouncing between 00 and 12. My EGR valve has 12K miles on it. I've seen it work properly before when I had a different tune loaded in my PCM.

Using Tunercat, I looked at the ECM constants and saw that the EGR enable min/ max rpm were both 6375. I set the min. rpm to 900 and max to 2500. Now when I cruise, it doesn't bounce back and forth, it just stays at 00. My cruise rpm is between 1500 and 2000 rpm.

The min. MAP is set to 36.2 kpa and my MAP while cruising at 60 mph was around 55 kpa so that's good.

The "EGR enable cool. temp (hi startup MAT)" is set to 50*C and the low startup MAT is set at 82.25*C. Does this mean when it's hotter outside, EGR will engage at a lower coolant temp and when outside temperature is colder it will engage at a higher coolant temp?

The IAT (same thing as MAT) was reading 54*F (12*C) tonight and my coolant was about 174*F (79*C). Should I lower the "low startup MAT" to a value below 79*C since that's my usual cruise temp?