237k miles
new/reman heads from dover
no cats
rear o2 sensor not hooked up
true duals running into a magnaflow
kand n intake

So when i fire up the truck it runs great cold. Once it warms up and you get going down the road it will start to miss when trying to maintain a speed of around 75 or if you give it throttle. no codes are being thrown. at idle it will miss as well after it is warmed up. any ideas? need more info? its almost as if someone is turning the key off and on