I just compared the 15-1994 and 15-2116 versions of the AMP/0331 code, button for button.

The following buttons all use the same codes (in each version):
VOL+
VOL-
MUTE
ARROW UP
ARROW DOWN

The codes on the numeric buttons were all moved up by one when they programmed the 15-2116 (ie, the '1' button on the 15-1994 has the same code as the '2' button on the 15-2116.

The SURROUND button on the 15-1994 is the SELECT button on the 15-2116, and the MENU button was dropped completely. The POWER button isn't defined in either remote.

The advanced codes for the 2 dropped buttons are:
072 SELECT
139 MENU

Here are all the advanced codes for AMP/0331:

EFC Function
024 Input: 0
059 Input: 1
171 Input: 2
182 Input: 3
026 Input: 4
166 Input: 5
022 Input: 6
164 Input: 7
020 Input: 8
170 Input: 9

230 vol up
234 vol down
228 mute

078 Arrow UP
082 Arrow DOWN
101 SURROUND
139 MENU
072 SELECT