I think it's something to do with the egr valve opening and closing at cruising speed/lower engine loads.
Not sure if this is correct:
1. At idle Egr opens to let crap exhaust recirculate
2. You accellerate off and egr closes and boost comes on (high egts)
3. You hit cruising speed. Ecu reads there's low (less than ~55%?? on scangauge) engine load and cruising. Ecu opens the egr valve (even though it's blocked)
4. Bosst pressure increases as more air is flowing??? egt lower
5. Accellerate (more load) egr closes, less boost, more fuel = higher egts
Sooo this happens even on a stock CRD. Try it...
Get up to 100 and cruise. When you are going slightly (less load) down hill you'll notice boost increases.(egr opening) EGTS go way down as more air is flowing
Tap the accellerartor and egr closes and boost goes lower and egt rise as more fuel is being pumped with less air.
Bigger exhaust just makes the boost value slightly higher
Then the EGR block raises the boost even more.
Just what i think what happens. Might be wrong.
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