Civic EG

Hi, I have d15b2 in my eg and fuel economy is bad 10 liter per 100km or 23-24 mpg.I've checked timing ignition, changed fuel and air filter and timing belt.When I start the car it starts normal but I have poor throotle response and acceleration and chooking problem.

Does the o2 sensor appear to be fouled (covered in black soot?) I've had them get like that and function enough not to throe a CEL code, but throw off the air/fuel reading to the ecu.

Some news, I've changed spark plugs ngk and new denso O2 sensor and now is everything ok