Ok, got an 06 dually, with smarty revo on 3,timing 1, wastegate off, torque on 2, and rail pressure default, with *****'s intake, ats arcflow, and 5" straight pipe. Its been doing something weird lately when towing. Driving empty it runs fine, makes 40 pounds of boost easy and has tons of power. When I hook onto a load, it runs fine at first then as soon as I have to get on it on the highway or something, it will go up to 35 pounds of boost, then the exhaust will change tone, and the boost will drop to 30 and just start bouncing there, and you can hear the engine pulsating too with the boost gauge. The truck loses power completely and just will not go. Egts climb to about 1400 also. All this usually happens around 70mph and only with a trailer on. I was hauling a load of 26 round bales down to fort davis the other day and literally slowed all the way down to 40 cause my truck just wouldn't pull, and egts were too high to stay in it anyway. Then if I stop at a gas station and kill my truck or something, then get back in it, it will run fine until I get on it again and hit that 35 pounds of boost mark, and it starts all over again. Anyone have ideas. I've owned three, all set up just like this, and havn't ever had this problem. Thanks

 

your boost is over-riding the spring pressure to close the wastegate.
When that happens you have to stop the flow or slow it down a lot to get it to close again and then you can run up to 35 or whatever it is when it opened.
Common problem, new wastegate or add a spring to it.

 

Oh ok. That makes sense. I thought maybe it might have something to do with the wastegate, but just wasn't sure.