Here's the page from the mot manual...

check out the box in bold text at the bottom right...
it can be downloaded from here.... probably worth printing off and sticking in your glovebox before the test.
http://www.motuk.co.uk/images/non_cat.pdf
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Yeah it's the HC reading that's the killer for me on the IDA.Lucky wrote:Just wanted to say thanks again to Ian and this excellent forum. Just had the MOT on the FB and took the page from the MOT manula along. The tester's an old mate anyway, but he freely admitted he had no idea this clause was in there. He showed me the on-line PDF of the manula all the MOT stations get sent, and that section 7.3 is about ten pages of text. The flow chart above doesn't even fit on one page, you have to scroll around it on the screen, and the little box-out clause about rotaries doesn't appear on the page, you have to actually look for it! No wonder so many MOT emissions tests are being done wrongly on FBs.
In fact, the last test that my FB had was done (wrongly) under the "pre-1986" clause of the flowchart, and we put the probe on it today just out of scientific curiosity. It passed anyway; 2.73% CO out of 4.5% and 335ppm of hydrocarbobdoodads out of 1200unfcknblvbl
Bloody hell