99 Cirrus with mysterious problem
 

Ok I bought this 99 Cirrus for my son about 2 weeks ago and have had nothing but problems with it. The strange thing is the dang car runs well but has what seems to be 2 aggravating intermittent problem. First day he had it the car would die when he would slow down for stop light/sign and the oil pressure AND check engine light would come on. Took it to our mechanic who got a code off it for the EGR valve. He replaced the oil sending unit and when he went to look at the EGR valve found out that it and some of the other hardware with it had recently been replaced by the last owner. He checked some of the lines to the EGR valve to make sure they weren't clogged. A few days later the car was still dying intermittantly or while driving it around 40rpm it would sputter and with both occurances the check engine light would flash on for a second or 2. The car always starts right back up after. Well we assumed it was throwing a code but when we took it to auto zone last night the man there said he wasn't getting any codes on his scanner.
The second trip to the mechanic cost me $425 for a distributor and rotor to no avail. Not 15 mins after we left the garage it started again. This is the 99Cirrus LXi v6. Does anyone...please....have any idea what the hell could be the problem with this car?