I’ve been using an MSD box and Axcell super coil for the last 7 months and I love it. They were good for a 2-mpg increase apiece (4 mpg total). The extra mpgs weren’t really a big deal, but it felt like it had noticeably more power. The coil smoothed up my rough idle. I’m just using the MSD 5 box (the cheap one); I have no idea if the 6 is any better. You don’t have to modify your distributor, but you do have to cut an ignition wire (the instructions explain it all). It only took me a couple of hours, but any competent person could do it in a ½ hour or so. Electrical wiring is not my strong point. I’d do the mod again in a heartbeat. BTW how old is your cap and wires? They are pretty cheap and it probably wouldn’t hurt to change them if it’s been a while. New spark plugs help too. I prefer Bosh 4 prongs, but any good platinum tip one will do.