Rockman 2 Energy Speed Data by Yave Yu.
This document will help you to change energy charging speed.

Rockman/Mega Man:
$3831B is HP charging speed.
$3835A is Weapon charging speed.
$352B2 is E-Tank charging speed.

Boss:
$2C142: Early 8 Bosses' energy charging speed.
$2E12B: Later Wily Bosses' energy charging speed.

Miscellaneous:
These are not energy but uses same speed system.
$37C51 is equip text printing speed. ($37D4A for Mega Man 2).
$35994 is path appearing speed in Wily Castle Map.

Value:
In original Rockman/Mega Man 2, $3831B, $3835A and $37C51 are uses 07, other are 03.
00 is fastest speed. (e.g: AB)
01 is faster speed. (e.g: NC, GZ, ONN, BM)
02 is faster speed but not very smoothly. (e.g: DEM, Claw)
03 is normal speed.
04 is fast speed but unsmoothly. (e.g: GX)
07 is slow speed.
Other are strange unsmooth speed.