1. Why do you believe it is missing 10 HP?I know this is an old thread but I wanted to post the easy solution. Last month I installed a 2008 titan VVT motor in my sons 2004 Titan, I extended the original camshaft sensor harness from the rear of the motor to the front of the motor and connected it to the cam sensor on the front of the motor (was on the rear of the 2004). Runs great but I'm guessing were missing out on that extra 10HP somewhere. He has been pulling a trailer with it an no problems. It doesn't throw a check engine code I'm guessing because the ECU isn't able to predict the future invention of the VVT (since it wasn't used then). Hope this helps someone.
2. Is it still running OK?