2002 Hyundai Elantra why does my car hesitate?

My car is acting very strange. The engine wants to quit on me. It keeps stalling. When I am driving, the engive willl cut out for a few seconds and if I keep the gas on, it will like restart... It is hard to explain but it is almost like it shorts out. I have had cars not idle for me but this is different. It just dies
even when I am applying the gas to it. doesn't matter how fast or slow I am going.

We recently removed the catalytic converter because it was plugged and just put in a straight pipe. Could the two be related somehow?

Thanks for any help you might be able to provide. I know it is kind of vague but not sure how to explain any better.