This thread is long and usually displays on several pages.  Your post is #96, and that info is written just above your user name.  You can navigate between pages by using the controls near the top and bottom of each page.

It's also important to realize that Comcast uses two different IR signal protocols.  EFCs beginning with 00xxx are used with setup code 01376/00476.  EFCs like 39877 are used with setup code 01982.

Exit is 39877
MyDVR is 43205

For example to assign MyDVR:
1) Press Cable
2) Press and hold Setup until 2 blinks
3) Enter 994 (should see another 2 blinks)
4) Tap Setup (don't hold it.)
5) Enter 43205
6) Tap MyDVR
The remote should blink twice to indicate that it recognized the procedure.

Now MyDVR should work.