Guys i have a question a few years ago,i got a few jobs done on my z,the mechanic said that the cats were bad on the car,78000 km on the car,At around 1,500 to 1,800 rpm while revving on and of the throttle i get a banging from the exhaust,it seems it coming more from the middle,would anyone know what this might be,And also it doesnt seem to idle properly,the car drops down to 600rpm and then jumps back to 900 then back down again,keeps doing this.I have uploaded a few vids sorry for the bad sound quality.Any light on the subject would be great,Thanks 

 

 

It does sound like the cats are rumbling and a blow somewhere from the middle, if they are the original cats like mine were, prob best to change or take off and look at the system, you can’t see much until the exhaust has been removed. The Rev drop could be many things search for rev drop on that question.

hope this helps. 

You could remove the down pipes and gut the cats. Just to provide an answer. Either way it sounds like you have an exhaust leak down there. 
There’s a long list of things that could be causing that stuttering though from boost leaks to faulty components. Have you done any diagnostics? 

1 hour ago, Stephen said:

You could remove the down pipes and gut the cats. Just to provide an answer. Either way it sounds like you have an exhaust leak down there. 
There’s a long list of things that could be causing that stuttering though from boost leaks to faulty components. Have you done any diagnostics? 

No i havent done a  diagnostics as my cable isnt working for some reason,i found alot of leaks around 10 leaks but just cant find the last one,Seems to me that is is leaking from the  plenum ,have a new gasket but the thoughts