I understand that to get the best possible performance uplift with the Hiper, I must bin the cat. What are the implications of this, apart from the obvious emissions problem at test time.

Has anyone actually got their car through a test without the cat, that would be interesting.

Also, if I were to replace the cat with just a length of pipe, what happens to the lambda sensor? you can just leave it tied up somewhere surely. Does the replacement pipe have to have a stabbing for the sensor?

Any advice would be most welcome.

Thanks guys

I think you mean the pre-cats. You'll get throught a test with no pre-cats on. From what I believe its impossible on the lexus to remove the main cat.

I have removed th main cat but still have the precats. The improvement is great, only negativepoint so far : check engine light comin up when in traffic jam with hot weather due to pollution level too high.

be careful they also do on the spot checks at the roadside