Egr codes cm 870 after rebuild

[Benjamin9669]

Egr out of calibration.
Truck runs like a dream after rebuild. At idle it will whistle stop whistle stop whistle stop followed by a check engine light and than it will go off, than going down the road it will boost 36-37psi in 13 or when it boosts a bit it’ll throw a cel. But the only codes is for egr. Main one is egr out of calibration. Maybe rawze would have some input on this?