I have a 2005 volvo s60 2.5t, recently replaced the fuel pump in it, i never had a check engine light untill I replaced the pump, I put a code reader on it and it read that my fuel pressure regulator was bad and that I was getting too much fuel. So I replaced the fuel regulator and still had the check engine light on, i rescaned the codes and the same codes popped up after a brand new fuel pump and regulator, the check engine light was on untill about a week ago and it disappeared after I reset the battery, now my main problem is that it acts like it wants to stall under low Rpms, and it doesn't do it all the time, it never completely stalls it literally just has no ***** until l you let off of the accelerator for a few seconds and then it'll launch. I'm not sure what my issue is, also every now and again I lose my fuel gauge completely untill I restart the car. I have absolutely no idea why the check engine light disappeared just from reseting the battery because I physically cleared the codes after replacing what I did and i also reset the battery. Could I be having a problem with the computer for the fuel pump?