Install and run Titanfall without a disc

I had the same problem, and I really have no idea why it happens or how to fix it. I have, however, found a workaround. I tend to just do this from the get-go instead of actually using the setup, because of weird issues like this.

1. Don't run the disc setup; instead, activate your CD key manually, and abort the actual installation process.
2. Open the backup window (Steam → Backup and Restore Games…).
3. Select Restore a previous backup.
4. Browse to the drive letter of the installation disc.
5. Steam should tell you that it found a backup of Modern Warfare 3. Click next.
6. The game will install from disc.

This has worked for me with MW3 specifically, and other games.

Note that you can't entirely avoid downloading it; you'll still have to download the latest patches to bring your game up to date.

This means two things:

1. If you cloak and then double jump the two blue exaust plumes won't be as visible.

2. Your footsteps make the same noise as if you are crouching, but you can sprint.

(2) is very useful in hardpoint matches when opponents are dug in, as you can sneak up on them more easily.

(1) is very useful when jumping about round titans - you'll still be pretty much invisible when double jumping to rodeo.

When you rodeo a titan they can hear your feet on the roof. They don't get the on screen warning until you pull the hatch off. As far as I can tell the kit doesn't make any difference - I've jumped on titans with the kit and they've electric smoked or jumped out before I've pulled the hatch.