99 Cougar, I HATE you! Help...

[FargoLuke]

Hello all,

We are at whits end with this 99 Cougar. Between work done by me and the shop we think we bought a lemon.

History. (6 Months Ago)

Replaced Upper and Lower Intake manifold gaskets
Replaced Camshaft Position Sensor (Misfiring)
Replaced all O2 sensors
Replaced Intake Air Control sensor. ( I believe thats its name.)
Replaced Fuel Filter
Replace all Spark Plugs
Replaced all Plug Wires
Flushed and Replaced Coolant


Currently

The starter is not engaging the flywheel. Its intermittent, about %40 of the time. The vehicle recently decided to drop from 24mpg to 10mpg. The exhaust is very rich with the smell of fuel. It has a hard time idling while in gear, has a tendency to die once the block warms up. Engine and Coolant Lights are on and flashing. I've checked for leaks, coolant is full and clean. I took it into O'Reilly's and checked the computer. These are the Codes its throwing out.

PO175- System to rich (Bank 2)
PO172- System to rich (Bank 1)
P1132- Bank 1 Sensor 1 Lack of HO2S1
P1151- Bank 2 Sensor 1 Lack of HO2S1
PO300- Random/ Multiple Cylinder Misfire
PO420- Catalytic System Efficiency Below Threshold (Bank 1)

All these codes where thrown 6 months ago when we had everything fixed. If this is a biannual event I'm sending it down the river!
Thank you for reading, If you have any info It would be greatly appreciated!