what could be causing the smell and driving issues?

What is your question?

I have a 2002 buick park avenue that has been acting really jerky when it goes up to 35 miles hour. This started happening after we had the catalytic converter replaced, also we get a strong electric/plastic burning smell after a time that seems to be coming from the rear of the vehicle. It can be smelled in the backseat and in the trunk. What could be causing all.of that?

What makes this problem better or worse?

It is worse as the car runs for a time

How long has your 2002 Buick Park Avenue had this problem?

This had been going on for about a couple of months