AGR/VTG Solenoid Valve Replacement

Hello,
I removed the magnetic valves for the EGR system and the VTG adjustment while changing the vacuum hoses, and I may have mixed them up.

Is there a simple way to identify which valve is for the AGR (Abgasrückführung) and which is for the VTG (Variable Turbine Geometry)?

The design looks identical, and both are made by Pierburg.
One valve has a gray head (in/out connections), while the other has a black head.
Both have the designation 1HO 906 627 on the back.
One has the identification number 7.21903.20 on the back, while the other has the identification number 7.21903.25 on the back.

It's a 1999 Volkswagen Golf 4 TDI with an ALH engine.

Thank you in advance for your answers.

fgolf wrote:

One valve has a gray head (in/out connections), while the other has a black head. Both have the designation 1HO 906 627 on the back.

Hi,

According to my knowledge, the Grau Kopf part should still have an "A" after the part number, and that one is for the VTG.
Black = AGR.

What is the exact difference between the two valves?

Are there other membrane or reed thicknesses for the throttle cross-section?

myfisch wrote:

What is the exact difference between the two valves? Alternative membrane or spring thickness throttle cross-sections?

At least in the flow cross-sections, I was able to clearly determine this when I compared the flow rates of the VTG and AGR valves on a G3 AFN engine.
Whether the magnetic side and the spring might be different ->