On Introscope, there is Threads folder which consists of Active threads and some more folders. But there is no folder related to services used by my application.
How should i find threads used by my application and will it tell me exactly which thread is taking time ?
I would suggest to go-way-round.
You can monitor the response time of your service using other KPI's (Like webservice avg response Time etc).
Regarding threads, you can keep a check on the state of those threads whether they are in Blocked state, Waiting state etc. Morever you can keep a check on the thread count.
because threads are meant for your connection and smooth processing of the application. What you are getting as Webservice - response time will be more sensible than thread response time as one thread will be linked to many application components.
Hope it helps.