Sorry for the long post or if it's not quite your symptoms had a C4 RHR 18 months ago.

P0490 - Exhaust gas recycling electric valve position copy signal (Valve closed too much)
Valve closed too much [Not Present]

Replaced stuck egr valve & carried out re programing with dec.
But the surging remained.
What does your live data say?

My problem seemed to start from about 1200rpm light throttle.
The recorded turbo pressure rises above setting level, & egr is constantly pulsing fully open & closed upto about 3500rpm ( with high afm readings ).
If the vacuum to turbo wastegate is interupted there also is no pulsing because of the lowered air pressure.

0 rpm 736 rpm 2912 rpm Engine speed

681 Mbars 1001 Mbars 1363 Mbars Turbo pressure
1235 mbar 1001 mbar 1107 mbar Turbo pressure setting
0 % 87 % 65 % Turbo pressure electrovalve OCR
0 % 87 % 65 % Turbo position setting
27 % 71 % 65 % Turbo position copy
0 % 36 % 50 % EGR valve electrovalve OCR
0 % 36 % 9 % EGR Valve Position Setting
1 % 34 % 1 % EGR valve position repeat
9 % 9 % 9 % EGR throttle electrovalve OCR
446 mg/cp 207 mg/cp 485 mg/cp Air flow reference value
0 mg/cp 212 mg/cp 299 mg/cp Air flow measured





It was caused by the turbo position sensor.
It should be no more than 12% KOEO and go to min of 95% under full vac

Hope the helps..