Still getting some Trouble codes...? P1423, 1411 AND 0442

Hello all and first let me say thanks to all who have posted here, you guys and gals have helped me learn such and helped me save so much money working on my car. Here are the stats:
2000 B5 2.8L V6 FWD 5 speed
Vacuum lines and fuel filter replaced by my indie mechanic
CTS replaced by me last March
New ECM and battery
New plugs, wires air filter, Evap purge valve
181K miles

Here is what happens...fixed all codes I was having ( 1423, 1136, 1128, 0421, 0431, 0441, 0442) by replacing the Evap Purge Valve and cleaning the MAS and air filter. Symptom which prompted this was hard starting only after refueling, and research here pointed me to the Evap Purge Valve. Car ran great for 250 miles of pizza deliveries, but as a cold front came through and the outside temp dropped 40 degrees and I watched my temp gauge drop 35 degrees and then BAM , beeeeep and the dreaded CEL came back on. Checked the fault codes with my reader....1423, 1411, 0421 and 0431. Cleared the codes, and the car ran fine the whole next day as it was warm and the temp stayed at the normal setting all day. Then, this morning as I started the car for work the CEL came on again right at startup before the engine had a chance to warm up...1423, 1411 and 0442. I was wondering if my thermostat might be stuck open because of the temp involvement ( I have changed the CTS but still have the temp gauge show below normal operating temps when the car is operated below mid 40's temps, roughly. No/low heat and no defrost so I know I need to flush the coolant system, but am waiting to do this when I have the TB and water pump done.)

I am not familiar with using a vacuum pump to test my lines, but I have heard the SAIP start on startup and shut off shortly thereafter, but I should make sure I can get this same result now, as this was when I first bought the car with only 162K miles. I'm wondering, if the thermostat is stuck open, then is the ECM is trying to bring the engine up to temp by enriching the air/fuel mix, which causes the bank 1 and 2 too rich codes, and the CAT codes.

I have been researching things here, but thought I should post this and see what response I get. I have gotten a ton of help from this site and respect all who have posted here and helped me in the past.