My bike has been cutting out at about 60mph after about half an hour of riding for the past dozen or so rides. Today I was travelling on a dead straight highway and again the bike coughs, splutters, backfires, so I pulled in the clutch and coasted to a stop. When this all started happening I also noticed that the engine oil light came on and the speedo needle was bouncing all over the place. After I had pulled on the the side of the road and came to a stop the motor was running okay and all seemed to be okay again. I continued my ride for another 30 or so miles at about 80 mph without a another trace of a problem. Like I said, this odd behaviour has been surfacing each time I go off on a ride, and it seems that once it's done it's thing it goes just fine for the rest of the ride, then next time I go out for a ride I have the same hassle again. It's really annoying going for a ride constantly wondering when the demon is going to strike again and hopefully not result in an accident while I'm trying to negotiate my way to the side of the road again.
I have stripped, cleaned and reassembeld the Mikuni carb, checked fuses, bulbs, harnasses, battery, cables, connections, and I am wondering if it is a coil problem or an ignition module being troublesome. Question is how to check without replacing one component after the next. Can anyone offer any sound advice please. Thanks.  

Maybe this will help. I recently went to Fire and Ice run in Grants New Mexico.  Afterward my girlfriend and I went to San Francisco just for kicks on my 2006 Deluxe Softail.  When I got there we were ready to cross the Golden Gate and head back.  My bike started doing what you described,  No sooner I would pull over she would start running fine again, after a while this got anoying.  I took it into a Harley shop in Fresno California.  They found that a terminal on the ignition switch came loose, not compleatly but sliped off and still kept miminal contact, just enough to keep the system going after the terminal heated up.  It actully got so hot it melted the underside of the switch.  They replaced it and it ran and still runs great.  Good luck I hope you find the problem.
Steve