Alright, I'll make this as short as I can. I just fully rebuilt a fresh 4.7. I had a machine shop/engine builder do the short block to save time plus he's great. Right now the motors in, it starts, runs, drives, stops, no check engine or any codes. No leaks. HOWEVER, the left side head(driver side), no power. BARELY a rough idle. Smooths out with acceleration. When i disconnected the coils one at a time, no change to engine performance. What's tripping me up is there's NO CODE. I put my brother in laws crazy snap on scanner on it and that wouldn't even pick up a mis fire. I'm ruling things out right now but I'm stumped. If it was a valve I'm sure I'd hear a misfire. If it was timing I'm sure I'd hear that too. Please help mopar maniacs. Thanks

 

Injector issue. Even though its a new engine I would do a compression check.

 

I did and the compression was all over the place but it might be because of this crap battery drains after only a couple cranks. I thought about injectors but I'm pretty sure the plugs had a little gasoline smell. I'll have to double check. Do you know of the injectors have their own ground? That's where I'll go first. Thanks my friend

 

I think the ground is thru the PCM.

 

I would not rule out the short block but I would consider it one of the last things to look into. I would go into with this approach.
1. Make sure all your grounds are attached. Lack of a current carrying path can do weird things.
2. Go about this cylinder by cylinder. If you have access to a higher end scan tool see if you can disable cylinders one at a time in the tool to find the one that contributes the least. Isolate it to a cylinder or set of cylinders.
3. Once you isolate it to a cylinder check the injector, coil, and plug for that cylinder.
4. Don't overlook fuel pressure. Make sure it's not only building the appropriate fuel pressure but it's holding it after truck shutdown for the prescribed period of time. Fuel pump pressure issues can do weird things particularly if the regulator can't reliably hold pressure.
5. Compression numbers aren't super reliable at this point. Now no compression is one thing but a deviation of 20-30 psi isn't something to get super excited over yet. This is a fresh motor and it's possible the rings and such haven't 100% seated. While it should not deviate at all I would give it a pass for now. In a couple hundred miles yeah I would be alittle concerned.
6. If you cant find anything wrong and are 100% certain it's the motor then a leak down test is needed to determine where the compression is going. Don't blame the short block unless you know for sure the compression is going into the crankcase vs the intake/exhaust/cooling system. For all we know it could be a valvetrain issue or improperly torqued head bolts/headgasket if it's a motor issue.

 

The OP needs a factory wiring diagram for his truck but if I recall correctly this is largely correct. Plus many times there were 1 or 2 capacitors on this ground circuit to keep the surge of the injector firing off the pcm.