I agree with VG, need to check for pinched lines first. If that's not it, and you have same problem with wing off, I would then loosen the needles on the valve. Still does it, check for pinched line in the wing, (hand air pump directly to the airline), still no good, check for binding.
Guessing you have Robart valve?? I have had a couple of those that were VERY touchy, loosen the needles a touch and try it again. I've use BVM restrictors and never had a problem with them, just a piece of brass with a small hole in it. Crap in the air system will cause the same problems on needle valves, pinched lines (wheels collars) as it will restrictors