Won't help
The windscreen that came with the NT3 really won't help much with the cracks with the t's and p's, it's meant mainly to block some of the wind noise you would pick up if used outside.
What you need is a pop filter, these are specifically made to stop that sort of thing from happening without destroying the natural tone being picked up. You can buy them from most music stores from $20.00-$35.00 or so or you can make one from a coat hanger and some pantyhose. The homeade one would work o.k. but I would suggest getting yourself a nice pop screen to go with your nice new mic!! I got one and it helped immensely.
Another thing to try, if you haven't already, is to stand back from the mic, these things are very sensitive so you don't have to be right up on them to get a good signal.
