Help me to pass group 2`

hi friends!

i am a CA final student having only 3 papers to clear in group 2 . got exemption on MICS nov 08 attempt. this was my second attempt.

marks in other three subjects got reduced than my first attempt despite better preparation. im really perplexed as to what to do....

Costing - i had worked out entire study material and past year questions..any other book required

DT - i have T.N.Manoharan is that enough...... how many times should i revise

IDT - which book should i follow....coz i have failed only in this subject.