Hi eveyone

This is my first post.

So I live in South Africa and in '91 I imported a Camaro Z28 5.7i V8

Some background: when i recieved the car i was told that they had prepared it for using leaded petrol, because at the time South Africa did not have unleaded petrol. although it is pretty clear to myself that there was no engine tampering i have no idea how they did this, it runs smoothly on leaded petrol and on one rare case where i by mistake filled it with unleaded petrol it caused piston missing a lot, but that was along time ago.

quite recently it developed a miss in the engine and im not entirely sure what the problem is, i replaced the distributed cap, all the plugs and the plugwires. it has a problem whereby the 'service engine light' is permanently on, and will randomly switch off for a minute or so to which the engine runs perfectly. so bassed on that i figured that it could be an electronic problem.

i recently bought an equuis code reader, but all that effort went down the drain because it didnt work when i put it in.

my latest thought was that it could be a connection problem with the connector box that is located between the firewall and the drivers seat part of the car, it seemed a bit corroded and i was wandering if anyone knows where i can buy a replacement part for that, hopefully that will sort out my problems, but im not sure what the issue is.

please help, i love this car!