Manifold advice please.

[G5FTH]

Hi,
I have a noise like a blowing exhaust coming from my drivers side manifold. I replaced the gaskets and its the same. I bought "new old stock" manifolds from ebay but when they have arrived I notice they dont have a lambda sensor or a hole for one.
Other than this they are identical and obviously original.

Is it a case of cutting a hole in the manifold to braze/weld in a bolt for the lambda sensor or does anyone have any other ideas.
I could return the manifolds but they were a good price and I cannot afford to go down the stainless route.

Thanks guys.

[G5FTH]

QBee said:

You can remove precats at the same time. Mine cost £100 for the pair to be welded. Both were leaking.

Thanks, if I remove the precats will it not fail an MOT?