First I would like to say thank you guys for all the amazing information throughout this forum. Although this is my first post here, I have spent countless hours reading through threads and I have learned a great deal. I would also like to apologize about the length of this post ahead of time.

I actually have 2 separate problems I need some advice on, both of which I have searched and have found some information, but nothing I am positive fits my symptoms.

I have a 2004 2wd QC 5.7 Hemi with about 110k miles. Mods are a homemade CAI that was on the truck when I bought it years ago, Pacesetter LT headers that have been on for less than a week and a Diablosport Predator tuned with 93 octane tune (also for less than a week). 3.92 stock gears and no cats.

The first issue is the truck stalls, always after letting off the gas when the RPMs drop and most of the time after pressing on the brakes. This problem has been going on for probably a year and would only happen every once in awhile while coming to a stop. The problem has gotten worse since the LT header and has died about 5 times in the last week, twice while going around a corner. Just today I punched the gas to get through a light, I let off the gas to and it stalled as I am trying to turn through the intersection.

I replaced the EGR about 3-4 months ago and cleaned out the pipe really good. At the same time I cleaned the throttle body and intake pipes as well. Although I don't believe it is relevant, I have seen some posts on here suggesting this problem can be caused by worn brake pads or a bad speed sensor, so I will mention that the brake rotors and pads are fairly new as well as the speed sensor in the rear diff (the plastic broke a few months back). The best guess I have is maybe the IAC? I am hoping someone can agree with that so I can feel comfortable knowing that is the issue, or give me another idea.

The second problem has also been going on for a year to a year and a half and I pretty much forgot about it until recently as I just became used to it. Only from a stop, when I hit the gas there is a small thump you can feel. If you barely touch the gas (barely meaning just enough to get the truck to move slowly) the thump does not happen. I am unsure if this is an issue with the rear end or possibly the transmission. I was hoping to get 4.56 gears ordered next week and was hoping to keep the stock LSD for the time being due to the price, but I figure I need to fix this problem or at least identify it before I spend money on upgrades.

Sorry again about the lengthy post and thanks ahead of time for all the help!

 

I forgot to mention the motor mounts and transmission mounts were changed recently as well, so the "thumping" is not related to that.