I've been struggling with new Digital 6 Plus on my El Camino for a while now. Above 5000 rpm it gives me an inconsistent miss, like a cylinder gets dropped, that wasn't and is not there when I run it without the MSD. I'm running an older pre billet HEI and I've never replaced the coil in the cap. I've called MSD 3 times to get information and i keep getting the same canned answers, I've run the magnetic pick up wiring away from everything that could cuase electrical interference. I've changed the plugs, plug wires which are now the super conducter wires MSD reccommended, changed the cap and rotor, added a sheilded magnetic pick up harness that was reccommended, and moved the box from under the hood to the passenger side kick panel where the factory computer used to be and even returned it for a new Digital 6 Plus in case the unit was causing my trouble, it still misses above 5000 rpm. I've also borrowed a 6al from a friend to try in place of the digital 6 plus to see if the problem is i my car or the box, i have yet to test it, but i will this weekend. Any chance that my older coil is going bad and can't keep up with the MSD's power output at higher RPM? It seems to run fine below 5000 but I've lost races with the miss and I can't be consistent when it misses. When i run it without the box it runs clean up to my 6000 rpm shift point. Sorry for the long read, thanks for any help or insight you can offer.