1993 Chevy S-10 Code 43

I have a 93 S10 P/up 2wd 4.3 tbi z engine. The code I'm getting is for the knock sensor/ esc problem. This engine had the heads replaced before I got the truck, and I'm not sure of the knock sensor location or if it is correct. There's one on the back of the pass side head that has a 1/4 inch stud on it, ( smaller than the one from the parts store), the one one the driver side is in the water jacket on the side of the head between the back two cyls, and it has a stud larger than the one from the parts store.
Which one is the real Knock Sensor, and what is the correct part? The base timing has been set correctly, but it still throws code 43 and runs rich and rough, HELP!

By the way a "real" mechanic changed the heads because of an overheating issue. The freeze plugs were rusted out. This $100 truck is adding up.