The IC-910H offers a fast or slow AGC response selection from the front panel, this selection isn't very effective, and in fact AGC is always 'fast'.... In order to improve the selection of the slow response (eliminating the AGC 'pumping' under SSB operation), the R/C timing components of the AGC circuit must be adapted as follows: Remove power, open top and bottom covers of rig
on the underside, locate the MAIN UNIT PCB (it is on your right side, with the front panel facing to you, and doesn't need to be dismantled)
replace (or just solder as piggyback on) R312 and R914 (22k original value) by 2.2 k resistors, SMD or 1/16watt version.
replace C910 and C306 (originally 22µF) by 47µF/16v electrolytic type To locate these components, you will need the service manual which is downloadable from different internet sources as a pdf-document.