92 Buick Hesitation

I have a 1992 Buick Park Avenue with 142,000 miles on it. I changed the plugs for the first time (for me) as I bought the car used. The plugs were very corroded and rusty, otherwise looked O.K. They were hard to get out. I put in new plugs gapped at .060 per the manual. I now have a slight hesitation and popping noise when I accelerate. The car seems to idle O.K. What did I do wrong? What can I do to correct the problem? I also put in anew PCV valve and changed the oil. That was it.

Thanks, Carljavascript:emoticon(':)')