2002 Chevy Lumina car dies

2002 Chevy Lumina mileage: 60,000. I have just purchased quite a lemon and I am on the brink of deep sixing it. I have seen other articles here with VERY similar symptoms, so I apologize for a repeat, but here goes FP is 40#, new MAP sensor, new IAC Valve, new EGR valve, new O2 and new injectors and regulator. Two problems. The car starts very well, hot or cold, idles pretty good when cold however pretty rough when hot. The idle when the car is sitting still is about 550RPM, but if I let the car roll in neutral 5-10 MPH down hill, the idle jumps to about 2000 without touching the accelerator (note - it also smoothes out). Once I push the brakes and slow the car back to 0 Mph the idle settles into a rough 550RPM or so. If the car is stopped and I rev the engine, it gets to about 5000 (or so? No tach) and starts to cut out, 5000, 3000,5000,3000 etc. It doesn't seem to do this if I get up to speed (55) and let it coast in Neutral and rev the engine. This symptom is very consistent and reproducible. The second issue is occasionally the car flat out dies. When it's cold and I can stay moving (i.E. Freeway 55MPH and no traffic) it runs great. Once I have stopped a few times either in traffic or just around town, it will die unexpectedly. The only recourse is to put the car in neutral or park, turn the key off and start. It always starts right up. It does sometimes die again immediately after starting, other times, away I go down the road. When the car dies while going down the road the speedometer drops to 0 immediately, but if I switch the key off and on, the speedometer catches back up even with out the engine running. Computer glitch? For either case, Codes 34 and 44 appear on occasion. Any help on either or both of these problems would be appreciated.