Well, last weekend i put two high flow cats on my car, now yesterday i was driving and my CEL comes on. I get the code read and its P0153. I cleared it and it came back again today.I know its for the upstream sensor on bank 2, and itsfor aslow circuit response.Is there any way to fix this, or do i need to buy a newO2 sensor?

 

That's an O2 sensor "slow response" code, could be a failing sensor, crossed or shorted/open signal wires, an exhaust leak near the sensor, etc. [/align][/align]Check the connections, maybe something got dislodged when you replaced the cats...[/align]