Interesting 8 pin HEI issue

Ahh, the good old 8 pin. I found this out the hard way. I read up on the GM HEI module swap and decided i wanted to try it out, so i went to the junkyard and got the 8 pin module and coil and gutted my old mopar ECU and put the 8 pin module inside, got it going and kpt getting ping at WOT and couldnt figure it out, so i hooked up my timing light and watched..with the 8 pin module, it would advance the distributor an additional 10 degrees of what i had the mechanical at! Long story short, i ended up having to go to the 4 pin module to stop the extra advance. I did keep the coil that is found on the same vehicles that have the 8 pin module, so it works just fine with the 4 pin.