1987 Pontiac Firebird V6 2.8l

My 1987 pontiac firebird v6 2.8l is still stalling on me. Stalls about 4 times in a row and sometimes the “check engine” light comes on and stays on. It also still has that knocking noise to it. My car only has 120,000 miles. When I accelerate my car jerks, bogs, and knocks. I heard it could be my timing belt? What else could be causing my car to stall and run rough?

so far I just replaced the spark plugs, spark plug wires, distributor cap, rotor, fuel filter, and the idle air control valve. So far this has cost me about $300 I was told by auto zone and car x to replace these parts, but the problem still continues...