knock sensor problems?

[four inch gunz]

hey new to the forum. was interested in purchasing a local dsm but the seller says it has knock sensor problems. i cant do the work myself (dont trust myself enough, heh), so what all could it possibly entail?
thanks

 

[girlieracr4g63]

Changing a knock sensor is simple. The question I have is this is a 1g im assuming? What is the car doing that makes the owner say that? Also is this car still stock?

 

[four inch gunz]

"catback exhaust and turbo xs boost controller"
he says it hesitates until you get on it.
thanks for the reply, by the way

 

[girlieracr4g63]

Is the check engine light on? The code for a knock sensor is 31..