I was having a problem with my jeep mis-firing, building up and then backfiring. Took it to the dealer after I replaced everything except the coil (thought it was ok about a year old). Dealer told me it was the coil. They took the coil off tested my jeep and it ran fine. Then they put the old coil back on and it still ran fine. I notice now that sometimes it starts hard and other times it starts up fine. I am looking to upgrade the coil. Any thoughts out there? What kind of work am I looking at to make an upgrade to an MSD coil or some other kind of coil? Would it be worth my time and money?