Dont drive the car with a BLINKING CEL on...Blinking means you have a catalyst damaging misfire, which means your car is running bad enough to damage your cat. converter....A new cat will run some $$$ and will cause your CEL to come on AGAIN.

Do a leakdown test. This will tell you how your valves,rings,headgasket are sealing up and can point you in the righ direction...

Did this problem start happening all of the sudden? Or after you had any work or service done?