Pls Help 1999 Range Rover 4.0 MIL light

[maysd]

I have read your postings on the 2001 Range Rover Check Engine Light

I have a 1999 4.0 Land Rover that is giving me these codes

I had the P0305 misfire code and replace all spark plugs and spark plug wires

I still had the code

I just replaced both heads because of lose valve guides and though that would solve the problems. The valve guides were in bad shape. Prior to the replacement I had the P0305 misfire cyl 5 code


Now I have these
I clear the codes. The engine runs fine until about 2400 rpm under load and no load and the I get these codes. I feel the engine miss and the MIL light flashes

P0137 O2 Circuit low voltage (bank 1 sensor 2)

P0305 cyl 5 mis fire

P1319
Misfire with Low/Empty fuel drive cycle C: signal out of range. Above Max

The dealer told me it was a slipped sleave in the cylinder. I have no coolant leaks and no coolant in the oil. I have no oil leaks.

What next. Coil? O2 sensor. I have a good OBD that has freeze data gathering.

any ideas, I love this car