thanks for all of the responses. I just figured it out last night. The neutral switch was something that i did test as well, as well as replace it with a good one off of a scrap car.
The symptoms were happening when the car was bought, which it didn't seem like a big issue, the guy said he had tried a few of the sensors which effect the idle but didn't get any to work. The car also had oil leaks and bad carbon build up due to not changing oil properly, it was more like it drained it or burned it off and the guy just filled it up.
I tore down the engine, did heavy cleaning inside getting it looking new which i also replaced the block because the one had some scratches in the cyl walls and i didn't want issues with it so i had another 2.5 block, and did head gaskets, water pump all seals, everything while the engine was out. the new block had a slightly different pcv system, it had a y splitter off of the crank breather tube one end went into the intake the other went into the air box. Different from the one that just went to the intake manifold. Not realizing what i had done until i had one of those moments, i essentially gave myself a giant vacuum leak whenever you let off the gas, making it sputter and throw the IAC code. So when all other hope is lost, look at the stupidest mistake you could have made during the install and fix it. Thanks for the responses, hope no one else makes this mistake.