Well, thats maybe because you introduced a massive f**king air leak into the intake system?
Use your SEARCH button, and you might find about 5,000,000 threads about this, and how we've totally hammered the f**k out of some people that just want to put a happy twirly duck whistle poofter call cop magnet vent to atmosphere BOV on their car.
If your lucky, there might be 1 person out of every 10 posters that will give you an explaination on why your AIR LEAK is causing the car to stall, etc, without being an ass like I did..