Truck shuttering

[78BO]

Hey guys,

Well the truck has 500 miles on it since the install. When I first started driving it I did not have any issues with the drive train. But here in the last few days I've noticed that when I come to a stop it shutters sometimes. It also does it when going into reverse and easing the gas. It almost seems to be slipping. I had the trans rebuilt before I installed the engine so it only has 500 miles on it as well. Any clues as to what it might be? I just had the kick down cable replaces yesterday. When I had it rebuilt I bought a new cable from advanced auto. But it never kicked down. The shop said buy a new cable form the dealer and it will fix it, I did and they put it on for free and it now works. I asked them if they checked the shuttering and they tried to give me some BS about it. And I quote “You know, because you have a high performance engine, it’s not going to run the same as factory. (right about now I’m laughing) He went on to say, the shuttering isn’t coming from the transmission I can tell you that.”

When I got in it to leave I put it in gear and the thing felt like it was a manual with a bad clutch. But it goes away as soon as you give it any kind of gas. Also at a stop while in gear I hear a deep ping, but it goes away if I put it in neutral.

Any help would be appreciated.
Bryan