CEL, need advice plz.

ok ive got a 97 lesabre limited with a v6 3.8l. I bought the car and it had a CEL on which threw a po305 so far ive changed the plugs and wires, as well as the coil for cyl 5. the light will come and go but as of late the cars been running really rough. i got it scaned and found po171-bank one lean, po305-mis cyl5, and a egr,tps code. ive changed the tp senor and replaced the exhast from the converter back. im prolly going to jus buy a egr valve and hopefully thats that. Id like to clear the CEL but dont have a clue what to do next about the mis and it running too lean. Any advice??

What about a bad injector or seal on cylinder #5!

Because of Age + mileage consider a smoke test for unmetered air leaks on PCV, EGR, injector seal,and Air Inake systems.