Had this Vectra 2002 JS II CD 2.6 V6 for years. Now the engine light stays on while driving. Got it scanned and was told that " catalyst efficiency below threshold on bank1 and bank2".

I used to have problem with acceleration hesitation problem. When start the cold car, it will hesitate while accelerating. But it will work fine after a minute. Now the problem just suddenly gone but engine light turns on. Is it something to do with air leak or exhaust leak?

Thanks very much.