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hi guys
i ordered a racing cat so now i would build a custom exhaust system but what diameter would be the best? 2,25 or 2,5 inches? normal steel or high-grade steel? in the moment my K8 enginge is totally stock without the silencer. In future maybe i will build the throttle body and intake manifold from a KLDE on my engine. Any suggestions?

Sorry for my english ;/ but thx for your replys

If your running your stock engine I would say 2.5" is too big.

2.5" is too large and you'll lose low end torque and probably be unhappy with it. 2" should work fine for your stock engine set up even with a few future mods. If you want larger, wouldn't go bigger than 2.25" inner diameter at most. Get stainless steel TIG welded mandrel bent piping done if you can afford to do it.

can i use only 2,5 if a turbo is running in my engine or what mods must i do so that is 2,5 inch is perfect?

i would say a turbo k8 2.25 and a turbo kl 2.5

Originally posted by BBK:
...what mods must i do so that is 2,5 inch is perfect?

Anything that develops 215 HP at the flywheel (not the road wheels )

hey thanks guys i have now ordered a 2,25 inch cat i hope it was a good decission