FUEL PUMP REPLACED NOW THE TRUCK BOGGS AT 40 ABOVE

I have an 03 Silverado 1500HD 6.0 about 165000 miles. I replaced the fuel pump because the truck wouldn't start. The truck now starts and runs since replacing it. Now the problem is if I hit the gas above 40mph the truck boggs but doesn't stall, it takes time to get to 65mph and doesn't have any passing power. I try to pass but it just takes it time. I took it to the dealer and he thinks it's either a bad fuel pump or one or both of the catalytic converters. No check engine lights are on anything else I might include on my search to fix this problem when I begin my search?