ok here's the deal, i have an n reg saab 9000cse turbo auto,

when engine is running it knocks on the right hand side and gets louder while driving, now i have asked a few people and have had different replies like it needs an oil flush and change to stop the noise or the big ends..... so my question is do i use some engine flush and change the oil and filter or do i just change the oil and filter as i have heard that engine flush will damage my engine and the car has done 137,000 mls so i am unsure if it is safe to use engine flush..... please help.....