all most 100% sure its your APPS mine did the same for a wile untill i replaced the whole thing.
1st scan for coads
if you get a p0216 and i beleave there is 2 others related to the apps thats your proplem
2nd if you do get coads dont try to adjust it, it will only get worse, I know and have seen it on others so leave it be till the new one gets there
3rd the best price Iv ever found is at ROCK AUTO its under emishion controle and is made by Air Tex(a good company) there way cheaper than the stealerships