Volvo: 2000 S80 2.9 L poor acceleration and gas mileage, gasoline consumption, oxygen sensors

Question
I bought my 2000 Volvo S80 non turbo with 68000 miles on it. I noticed that it has a very poor acceleration. I really have to give it a good step on the gas pedal so I can accelerate better. With that also comes the high consumption of gasoline. I always use 93 octane gas and I've even replaced my air filter with K&N filter but I never noticed any difference in acceleration and high gasoline consumption still continues. Any idea Vedat?  

Answer
Hello,
You should use 95 octone or more. You can dammage your oxygen sensors, and so your emission system may have faulty. My recommendation to you also, get your car's Electronic Throttle Module cleaned, it will be very beneficial for your car.
Regards...