Just started last night.....
Car seems ok up until over 100MPH in 5th when it starts spluttering and dying, (I was later told that yellow flames were coming out the exhaust when this was happening!).

Its ok if I back off a bit, I'm guessing some part of the ignition system isn't working right when its needing a good spark on heavy load, and the fuel's just igniting in the exhaust...

I replaced the dizzy cap and rotor arm just there with no change in syptoms.
Its a 2.0 pinto with a Lumenition kit.......

Any ideas people?!