I've got a question about the differences between the 80-81 heads and the 86-87 heads. As far as I can tell the water jacket has a restritor in the 86-87 and not in the earlier. also the EGR passage is different. I had a nice pair of 80-81's that were ported and had the Manley swirl valves installed and I put them on my 86 Gn motor thinking these were the only differences. Did I goof???My GN surges whenever EGR is applied and has always had a miss that won't go away. Feedback is appreiated