Stuttering at low RPMs

[fri3dchick3n]

I recently got my tranny rebuilt due to the lack of flushing the tranny fluid :\. I am the third owner but I do want to start modding my car slowly. After the tranny got rebuilt the car of course was driving fine, I was happy. After two weeks or so after, I noticed my car had trouble starting, I wouls start it up, the RPMs would go up then drop suddenly and the car would stall out. This was happening til the point the car wouldnt start anymore. I did some research and I decided to bypass my fuel pump resistor by bendint the tab 85 "i think" out and the car fired right up. But I did notice that my car is lacking some horsepower, I would have to put more pressure on my throttle for it to actually go somewhere and I figured that it might be the spark plugs. So I did changed them out with some NGKs. The car started driving like a champion but then it wouls studder as the RPMs get low. My first instinct was to give it some gas to up the RPMs but just more studdering, I would have to ease off the gas and wait a few seconds, then I can keep going. I noticed that switching from D(Drive) into 3 if im going over 50 would help because the RPMs would go up. I tried giving it some gas to speed up a little bit but feels like there is something stopping the car from going over 4k rpms. My engine light has just turned on today(finally!) I have not scanned it just yet, I am in a secluded town away from home at the moment.
Wondering if anyone has any suggestions on what it might be. Sorry for this whole essay but I really wanted to add as much info as I could. Any help will be great help. Thanks in advance.

[BillBoost37]

Sounds a lot like a vacuum leak at first. A big one.

How old are the plugs/wires?

[01gpgt01]

I bet the codes a lean bank code and you have a vac leak. or maybe a multiple misfire code and maybe you need some new wires

[fri3dchick3n]

Ok, so I scanned the car from NAPA. Said the 6th cylinder was misfiring. I checked the plug and the plug was very loose, I uncrewed it by hand. Before I could see the plug of course I had to drop it down the engine bay. But I bought another one and replaced, took it for a spin and it fixed the problem but with still very little vibration at lower rpms. Now just drove 200 miles and pretty much have the same problem now again, I will check the plug again tomorrow but I think I might have to change the wire aswell. And these garbage Alaskan roads arent helping at all. And a few mentioned a Vac leak. What do you guys mean by that? Thanks once again.

Update: I checked out all of my plugs, they look fine but a little dirty for how new they are I think. Time to do some research on a Vac leak. Hopefully it isnt anything major!
The wires are about 8-10 Months old and the spark plugs are 3 weeks old.

[fri3dchick3n]

Ok I checked out the Vacuum line to the throttle body, It looked just fine but I wanted to check it out, Thinking it was rubber I was twisting it and pulling it slowly and it broke like a cracker. Having some trouble finding black tape but I checked out the hose and it looks fine. I want to clean out the MAF but it is barely over a year old I think it should be fine.

[fri3dchick3n]

Alright I got a chance to scan my car and it pulled up the error code P0300. Random misfire detected. Im not sure what might be causing this problem. Anyone else have this problem before?

[logan809]

Check for coolant in valleys below your supercharger. I'm having the same problem and I'm in the process of replacing my lower intake manifold gasket. Your symptoms sound identical to mine. Are you getting bad mileage?