I was going to agree that it could be a faulty MAF or air meter, whatever it is in those cars.
But issues could also be in the fuel system.. fuel injectors, fuel filter and even your new pump. I've heard MANY stories of people simply getting bad Walboro pumps all together.
Oh, I haven't just heard about bad pumps, but I happened to have dealt with a bad one personally that drove a couple of my friends up the wall.