1999 Chevy Suburban on the side of the freeway.

Help! I have a 99 Chevy Sub with 247K mi on it and I'm having trouble with what I thought was a fuel problem. But have learned otherwise. My Sub is acting like it's starving for fuel or overloaded one of the two. Spits and Sputters when I accelerate. At first it was just once in a while and it would catch up with itself. But now, I can't trust it to go down the freeway, I have done a complete tune up. I have removed the fuel pump and checked the filter all is good there. The Sub acts likes it's not getting fuel or possibly it is a combustion problem. Recently it was making some clanking noises. Those noises stopped and then it sounds as if I have no muffler. Could the muffler, stalling, clanking, sputtering, all be due to the catalytic converter going out? Or do I have an ignition problem? At a loss - need the vehicle please help!