Whats the effect of removing the cats

[bmw540]

I think my cats are blocked which is causing my rough idle. What is the negative and positive effects of removing the core of the cats so they look standard but have no center.

[markus]

id jsut get some aftermarket ones welded in.

[hoser]

like these, if you're willing to spend about $150:
http://performance.drivewire.com/getparts/index.aspx?pdef=Catalytic%20Converter|Bmw|540I|199 5||||||Exhaust%20System

But you might be able to find some cheaper universal ones. I haven't found any though.

You can roll with the cores removed no prob I think, you'll just be making more smog. But if you can live with that, sweet.