I am having problems accelerating over 3.5k RPMS, Check says I need to replace O2 sensor, but I just replaced sensory 1 almost 6 months ago. At about $300 a pop, I cant afford to keep replacing em. I am wondering if the O2 sensor is the problem w/ acceleration, and if so why is the O2 sensor crapping out on me again? What would be causing it to blow?

Thanks for any help.