I replace my old 305 with a new 350 and replaced the knock sensor with a 350 but now i have been reading that the "knock module" must be changed too. Where is it. Is it one of the 3 relays on the bracket behind the brake booster on the drivers side firewall. If so which one. I took the bracket off to mount my MSD and the 3 relays are just tucked in under the booster. They all look the same to me. This is for a 91z28 350tpi

 

You're SOOOOO close! It's not the relays and not square. It is tucked up next to the brake booster right near the relays you are talking about. Sorta flat, weatherpack connector, nothing that would catch your eye.

 

do all tpi cars have this module? I tried getting one at the parts store and they couldnt find it in the computer. ALl that came up was the sensor/Is this a dealer only item.it is for a 91z28350tpi

 

AC/Delco Part#16128261 if that helps.(for 350)
Bought mine at a dealership.
Cost about $60.
-Rich-