1993 Suburban 160k knocks and looses power under load or acceleration. It starts and runs fine otherwise. What is going on?

If you are hearing a knock then you may need an overhaul. Run a compression test to verify wear on the rings and cylinder walls. A knock can also be worn piston pins, crankshaft rod bearings, or a cracked rod. This can be serious and needs attention ASAP. Now if what you are hearing is pinging, then that can be carbon buildup, or the timing may be off. ------------ Your problem could also be a stopped up fuel filter or a weak fuel pump. When you accelerate and the fuel pump cannot supply enough fuel, the engine will buck and ping and lose power. When you let up, the fuel flow is sufficient for the engine to run normally again. Start with checking/replacing the fuel filter.