When I put the Jacobs system on my mustang, I accidentaly didnt tie one of the wires up and it drooped down on the headers, and the wire melted through and shorted out thus ruining the Jacobs system. I put a MSD 6A on it after that due to $$$. When I changed to the MSD from the Jacobs, it lost 2 MPG......But that was with a 302 in a mustang.....Not a 460 in a truck.