why does my car stall in neutral /low rpms

What is your question?

I drive a 2004 Volvo s60. when the clutch goes in, rpms just drop like a rock down to about 400 which gets the car to shake like it will stall and then it will stall out sometimes. this happens when the clutch is in or when I'm in neutral. when I come to a stop in neutral and the car is running, the rpms go back to normal idle. it idles fine when parked. I just replaced the MAF sensor a week ago since I was getting 2 codes. p0101, p0171. faulty MAF and engine air to fuel too lean or whatever (too much air) when I replaced the sensor and wiped the codes, it still ran like the problem i described but the codes never came back up. Its been making driving a little more difficult since I cant really rev match when the rpms are tanked like that. It is a 5 speed by the way. I appreciate your time reading this. Thank you.

What makes this problem better or worse?

higher speeds and i put it into neutral it almost without a doubt stalls. I have not noticed anything to make it better.

How long has your 2004 Volvo S60 had this problem?

since ive owned the car (a month ish)