My car seems to be running very well,but just like the guy who finally got the right glasses to wear,it's hard to tell what improvement might be enjoyed.My car has several mods,including a mild 501 cam,and at 120,000 miles,my ignition is still all original and never serviced.The car starts easily,feels very strong,but except for an MSD coil,new wires and plugs,the distributor has only been opened once,twenty thousand miles ago,and only for a look-see. Could I actually be experiencing missfires and a power loss without really knowing it? Strong as it runs, I think some smoothness could be missing,and I would hate to know that I am not getting all that the engine has to give. So, has anyone replaced their cap and rotor and become "stunned at the new power and vitality" gained to what was thought to be a well running machine to begin with??? I'm also wondering if MSD is not better than Summit brand replacement parts, feedback please! thanks , edman