1999 Chevy Camaro

I have a '99 camaro super sport and my car will hesitate, but not always, it only seems to do it when I'm going up hill and lugging and give it some gas it will hesitate. Also, when it idles you can hear it hesitate or surge. I've taken it to dealership 4 or 5 times and they can't seem to figure it out. At my last visit they told me I may have water in my gas. I used heet and still have my problem. I have replaced my plugs and wires, fuel filter in the past year. They told me I had a miss on plug #2 and #7. I also have had my catalytic converters removed and was told that could be my problem? I was just wondering if you had any advice, this problem is driving me crazy! Thank you.