Yes, the refresh rate is adjustable in:
...\Prepar3D v4\SimObjects\Airplanes\CS_B767-300ER-II_PW4060\panel\panel.cfg

[VCockpit03]
size_mm=1000,1000
pixel_size=512,512
texture=$cs767_11_T
background_color=0,0,0
gauge00=Captain_Sim.y763.sys!adi_l,          0,   0,1000, 952, 0

[VCockpit04]
size_mm=1000,1000
pixel_size=256,256
texture=$cs767_12_T
background_color=0,0,0
gauge00=Captain_Sim.y763.sys!adi_r,          0,   0,1000, 952, 5

[VCockpit05]
size_mm=1000,1000
pixel_size=512,512
texture=$cs767_13_T
background_color=0,0,0
gauge00=Captain_Sim.y763.sys!hsi_l,          0,   0, 766,1000, 2

[VCockpit06]
size_mm=1000,1000
pixel_size=256,256
texture=$cs767_14_T
background_color=0,0,0
gauge00=Captain_Sim.y763.sys!hsi_r,          0,   0, 766,1000, 5

[VCockpit07]
size_mm=1000,1000
pixel_size=512,512
texture=$cs767_15_T
background_color=0,0,0
gauge00=Captain_Sim.y763.sys!eicas_u,        0,   0,1000, 965, 5

[VCockpit08]
size_mm=1000,1000
pixel_size=512,512
texture=$cs767_16_T
background_color=0,0,0
gauge00=Captain_Sim.y763.sys!eicas_l,        0,   0,1000, 965, 5

The less is any of the highlighted numbers the better refresh of a corresponding display. 

Captain Sim wrote on Apr 28^th, 2020 at 12:20am:

Is that value changes work for the most recent CS-767?
Patricio Valdes

Captain Sim wrote on Sep 16^th, 2021 at 4:48pm:

Many thanks. I am trying to improve the FPS since that even I replaced textures 4K to 2K I am still getting 3.7 FPS with P3Dv5.2 so, how to improve the FPS? I have another company and A2A birds giving me higher than 30 FPS and 40FPS loaded on the same EDFE scenery.
I appreciate to get some ideas from this thread.
Patricio Valdes