With Quieter Footsteps and (both: Audio Masking and Noise Suppressor on all weapons) I shot at a guy that was about 5 meters away 2 times and he still didn't turn to look my direction.
I love stealthy stuff and don't recommend any of the following unless you; as I did when i started playing EDO, have little or no experience in FPS content:
extra battery life or battery conservation
defense
shield regeneration
My goto move is: Maverick Suit: [Nightvision, Quiet Footsteps, Improved Jump and trying to figure out the best fourth option] and Sniper Rifle [Scope Enhanced, stability, Audio and Noise reductions] from a rooftop. It is surprising how often the sniper rifle works indoors as well; hence the Suppressor. Tormentor [extra ammo, Audio and Suppressor, Stability]
Ive begun experimenting with the Artemis Suit [Nightvision, Improved Jump, Quieter Footsteps & ???;] It is great so far. Can almost air boost across an entire settlement and it gives you more time to Air-Sniper.
Noise Maker: Gernade as someone said. Also if two people are fairly close together, sniper one and the other will get closer and pause a moment or two and you can sniper them too.
One word of caution: Military Base Guards always have their shields on, you need a headshot to guarantee a one-shot kill.
Ship: Vulture with shields, armor, basically as tough as you can make it. Some missions there are ships flying above you and if your ship isn't defensed up it will die. The Vulture makes a good Sniper's Nest too, has very, very small foot print which is important on non-settlement combat, recovery missions. I put 3 extra tanks on the Vulture to reduce Fuel scooping.