CEL Codes and a few questions

[Skully4]

Hey Toyota Nation people

well I have had a couple of 405 codes thrown at me by my 96 Avawife

Seems she to have no issues as long as I allow her plenty of time to warm up after resting all night.

So when she decides to have an issue it has been the excessive flow the 405/? the lovely EGR valve joke. BUT get this I remove the light/code

Now the really weird thing is my gas mileage has not gone down.
After I reset the code it stay clear for at times 1000 or more miles.
In fact as I said this weird thing seems to only happen if I take
off in the morning and NOT allow the car to warm up say go from 2000RPMs down to 1100rpms(5 mins)

Today took off temp outside was around 45 and as I am drivin
the check engine comes on..the car was like struggling to shift
see so I do not think this is a 405 code. It acted like it did not want to shift out of the gear it was in.

Then as I let off the gas an waited a few secs then pushed a bit on the gas peddle the check engine light came on .

So could it be a incorrect code?

Is there a connection between the transmission shifting and the egr?

Serious the gas mileage has NOT went down. The car does not act
sluggish or hesitate upon acceleration from a dead stop at a light.

The light has never even came BACK on after driving it all day .

This issue seems only to occur when the car is driven cold after sitting all night.

Ok Toyota people please share your thoughts
Thanks
Sherry/Skully4