NEED HELP car Idles at zero?

I need help fellas...well my 8g has been stalling during traffic, at stops, and low speeds...for the past couple months I have been having idle issues it will die at times when i slow down to stop ive been getting by...by putting one foot on brake and one on the gas....On the Highway at higher speeds sometimes i feel like it choked and stalls but then i gas it alittle more then it kicks back into running..i figured it was a bad IAC from the v6 swap...so i decided to change it back to the i4 TB and original sensors...

Now when i start RPMs go to 1k 1.5k then slowly drops down to 0 it idles on zero.. it hasnt stalled on me yet drove it around the house but im not sure having an idle at 0 is good... Ive disconnected battery before changing TB to reset the computer but it still idles at 0....I know that is not normal.. I ve been searching what it could be? but i see or hear any vacuum leaks, Manifold looks good... When i leave it long on idle and then shut the car off it does vibrate hard. I hoping anyone has any experience on this issue and can help me keep my 8g alive.... any input is appreciated...

it has 235k. and i dont want to start replacing parts just to eliminate them...Thanks in advance.

When you put back the gasket between the intake manifold and throttle body, are you sure you aligned it properly? Sometimes if it is misaligned it can cause a vacuum leak. Is the car throwing any engine codes yet? Make sure all the connections are good and you have not missed anything, like the hoses or MAF connector etc.

You did not happen to work on the gauges themselves? Also, the car couldn't actually be idling at 'zero'. Like Tamim said, be sure you have checked all connections, be sure wiring isn't corroded, or vacuum lines aren't leaking etc...

Thanks for the quick insightful replies...i double check again but right now my g is just parked for now.... If i can't get it running i might part it out... Thanks fellas

Have you done any other modifications?

No engine is bone stock went back to i4 TB... Its not throwing any codes right now even when it did stall no check engine i even got out my obd scanner.... Im not sure what it could be intake manifold looks good no cracks around TB... Just not sure if it's safe to drive with the idle at zero....like it rest on the pin.... Replace the aic 3x with some pick n pull i4 iac and still the same issue idle at 0..... Even if i open the idle screw all the way it will help it alot but the car would sound like trash it would idle 200 not even 500 then it wouuld go back down to 0 i had it running for like 10 minutes and car didn't stall rpm at 0? Weird?

SO i did something i shouldnt and i messed with the idle screw and loosen it... I got the car to run at or alittle under 1k rpm during idle.......i turn it way down and then loosen it as i saw the RPM rise.. i had 500 RPM but when i turned on AC the idle when to zero so I loosen the idle screw until I got 1K..and when i turn the AC its below 500 or at 500...I drove around town and it wasnt so bad...I also notice when i let my foot off the gas and coast when the RPM descended to zero it jump so did the car at times...and when I shut off the engine car does shake abit......is this something i should worry about ...Im throwing no codes and this car is at 235k.....I know idle screw shouldnt be touch but i dont mind bad gas mileage is there any harmful issues it can do to my car?