pretty sure blanking on a CF3 unit brings up errors, but yes, EGR valve would do this.
unbolt the EGR from the inlet but leave it connected to the car and then test with the software. you may find its completely stuck or at least sticking. clean it, clean it very well, then clean it again. don't clean it with WD40, you may as well urinate on a burning oil refinery (which I have done, incidentally) use proper carb cleaner or similar to do it with.
also check the VNT system on the turbo with software whilst engine is off. you want the VNT actuator arm on the turbo to be moving around 10mm if its not, or not moving at all then you are an airleak in the rubber vacuum tube and need to repair.
remember of course you can only test this with the engine off and it wont generate a vacuum so the more times you test this function the less effective the vacuum. if in doubt, fire the engine up, give it a slight rev and turn her off and repeat test. if its really not working them thats your issue.
1999 156 1.8TS Sport Pack 3
2001 166 3.0 V6 24V Super
2003 156 GTA 3.2 V6 24V
2005 156 1.9 JTDM-Jet Sport
2008 159 1.9 JTDM Lusso
1997 GTV 2.0TS Lusso
2001 147 1.6TS Lusso