My2002 Saturn L300 keeps shutting off

So do you have any code's?SO when you lose power does the car just bog down when when you press the gas down?Does it ever not shift unless you let off the gas?

Usually if you have to let off the gas for it to shift it's a clogged cat. So what are the exact code number's you have.

The clogged convertor can cause a stalling lack of power and make you have to let off the gas to make the transmission shift. The code P0421 is a cat code the p0128 is usually a bad thermostat. The P1780 is a torque reduction command. The P0727 is ENGINE SPEED CIRCUIT - NO SIGNAL. The code P0335 is CKP SENSOR CIRCUIT your crankshaft sensor. The p0102 is MAF SENSOR CIRCUIT LOW VOLTAGE mass airflow sensor. So did you ever clear the code's after you replaced all those part's?

So you replaced all that stuff a year ago or just the fuel pump a year ago?

So when shuts off while driving does it restart right away or do you have to wait for it to start.

So did you replace all these part's yourself?Or have someone do it for you?Because the stalling sound's like a bad crank shaft sensor the code p0128 sound's like a bad thermostat all the stuff you said you replaced.

Well the code's P0335 and the P0727 isn't going to a bad fuel pump.I have seen bad crank shaft sensor's set that code cause the car to die and have to wait til it cool's down before it start's. You can test the crankshaft sensor with a ohm's meter when it get's hot die's and won't start to see if it's bad.I find it really strange that the code's that are setting are the same code's that set most commonly from the parts that have already supposedly been replaced.I would have that crank shaft sensor tested when it's hot and won't start.I think I would find a new guy to fix your car because replacing all those part's and you still have those code's is not right.