Does the OP's warning light come on under ANY load conditions over 60? In other words, will it come on if you have your foot to the floor on the accelerator or if you're nearly completely off the accelerator, or doesn't it make a difference either way? Generally, if it's a misfire, it will be worse on very light throttle openings when the mixture is lean. If it does it all the time above 60, regardless what you do with the throttle, I'd be inclined to go for the phonic re-learn before cashing out on new HT equipment.