1996 Blazer 4.3 engine or either fuel problems

I have a 1996 Blazer 4x4 4.3 with 180,000 miles Just put in about 700.00 in ball joints shockes and getting alined and balanced. Also new radiator, theromstat and clutch fan. Now I'm having problems with once I get up to 45mph or higher, it feels like I got bad gas. I put some injector cleaner in it about a week ago. And still doing it, it comes and goes, but the farther I drive it and more it acts up like its cutting in and out with the rmp's jumping back and forth. I had someone hook up their computer but found nothing. I do know that even since I bought the thing if the gas get below 1/4 tank I hear this noise coming from underneath there the fuel tank is. Please any help would be helpful. I drive it everyday with my kids and need it get it fixed ASAP! Thanks!