V6 3.0 engine misses at 60 mph on slight increase in road level

spark plugs and wires check engine codes if there are any

Make model year??

Most likely if you have codes it will say misfire. Unless you have personally done the maintenance yourself, I can bet you that the three spark plugs on the backside of the engine haven't been changed out in years. Most places will only replace the ones on the front of the engine and tell you that they replaced them all. Major pain to change the back three.