Please Help!

Hello everyone. I have a problem with my 98 Tahoe. For a while now I have noticed a little shaking. It does not happen all the time, but it still happens. When I am at a stop I feel that my truck starts to shake a little. I also noticed that when I get on the freeway and I accelerate to go faster it will shake and hesitate a little. I don't know what the problem might be. I have changed the fuel pump and filter because they both went bad and it still happens. I had a tune-up done and it still does it. I have tried the fuel injector cleaner and it still does this. I don't know what to do anymore. Please help. Thanks!