There's a lot of info flowing here, and I am not trying to muddy the water.......... but I think there may be some terminology issue here, If your buddy is a auto mechanic what he is likely calling a high pressure carb fuel pump is 4.5 - 9 psi a low pressure is 1 - 4 psi ( in vehicle terms )
I say this cause I can see no way the needle and seat could hold 40 psi at all........ at that pressure it should be dumping a lot of fuel down the carb throat.....
I would still verify pressure with a gauge........ and would do as Chris suggests with a clear tube, cause I still think you have a lean idle condition.