What mod are you playing that has a Virginia?
Anyways, if you're in the stock version of the game, you can pile on speed in a Kilo and not really worry about it. Even at flank, you're still pretty quiet.
If you're playing in LW/Ami, then if you're in a Kilo Improved, you need to be judicious about exceeding 5 knots or so. If there might be a sub listening, stay slow. Same for if you think there might be a buoy field nearby, or if you spot and FFG getting too close for comfort. If you're in a standard Kilo, then you pretty much have to accept the fact that you are outgunned. Even at slow speeds, you're detectable, and if you crank it up at all you are very easily detected.
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