I have a P22 phosphor XD4 in a 14. Looking to get an amber filter to improve the eye strain issue but I don't know how well they work over P22s.

Based on a post here on ARFCOM they will cut light transmission, If I understand correctly they are basically high pass filters and given the orange color I'm guessing they have a cutoff wavelength at around 600nm. After seeing a graph on AiB website I wonder if they produce brighter image on a P22 over a P43 because the area pass 600nm is larger with the P22 curve.

Can anyone confirm this?

You will lose a lot of light, P43 has much more red component in the image than P22 does.
P22 actually has barley any of the lower light spectrum in it, its a rather cold colour.

The amber filters on the market today are carefully tuned in colour to get the most out of P43.

I have 2 ITT autogated NVDs: a PVS-14 with P-43 and a Sentinel with P-22. Amber filters on the P-22 do in fact improve contrast, just like on the P-43...but on the P-22 I give up a lot in overall brightness. I finally decided that the bump in contrast wasn't worth what I have to give up to get it and just took them off.

Are you sure it's P-22? Haven't seen P-20 or P-22 phosphors on (most) US made tubes since the Omni 3 era (not autogated).