2001 Dodge Intrepid Three engine codes found

Hello, I have been trying to troubleshoot one of these codes for over a year. The three codes are-

P1494- Leak Detection Pump Switch or Mechanical Fault beeen troubleshooting this for a year.
I have replaced the purge solenoid, gas cap, the leak detection pump and followed all the vaccum lines from the pump to the engine, cannot find any leaks. I also checked the electrical connections-no corrosion. All tight- I'm lost.

P1784- cannot figure out no such code

P0731-Gear 1 Incorrect ratio this is new about one week old or so.

I have erased all the codes after every new part installed. The check engine light will come back on within a day.

Now since the Gear 1 code the car will now stall intermittently at red lights or stop signs. Runs good otherwise. Please help cannot afford a repair bill.