Kilo is the most silent under 3 kts. At 5 kts it is same level with Seawolf and above that Seawolf is the best.
Kilo is detectable mostly by mistake of it's captain. With sealevel 3, you can hit it without noticing it. In such cases, check you HF sonar often
If you are in FFG, use active sonar (just time to time, few pings and the turn it off). If you are in sub, extend TA, be quiet, and be ready for that mistake.
In MP games Kilo suffers from this low speed and it also has small sensor range. Chances are big that it's captain will get bored and will go 10 kts time to time.
In 1 to 1 scenarios, with US sub, go active.
I played Kilo in MP several times with not much success. It's pretty hard not to make that mistake. In Kilo you have also weak torpedos, so it's hard to turn that stealthiness into victory.