HELP with knock sensor

I have a 1993 chevy g20 van that had the gulf stream conversion
it has a 4.3L V6

I can't seem to find where the electronic spark control module is?
It is not on the firewall, where the repair manual says it is supposed to be.

please email any answers to ccatlett1984@netzero.net

thanks in advance for the help

I ended up talking with 4 different dealerships, and one of them told me that there are 3 different 4.3L V6 engines that were put into this model of van. Two of them had the knock senor and spark control module, but one of them does not. On that particular model the spark control functions are carried out within the ECM

I have a 1993 TBI 4.3L Chevy G20 van and the knock sensor is in the back of the engine block (seperate from the control module) near the rear of the intake manifold (if you are in the cabin and remove the engine cover it will actually be closest to you on driver's side of block). You should ee a couple of wires coming into it. If my engine hump weren't such a PITA to remove I'd snap a pic of it.