A lamba sensor is always going to be on the pipe mate as it controls the fuel and air mixture needed for the exhaust. When you jump from cat to no cat some saxo's dont like it as their has been times were peoples rev counter automatically rises by itself, as the sensor has been used to having a cat but now differant the sensor gets confused.
Is your cat in the mani? is so you have quite a job on your hands and probs not worth doing unless you can get a dodgy MOT
If its on the centre section thats fine just get a standard saxo pipe that doesnt have a cat on it (think most mrk2) thats what i did on mine and easy enough to swap over for mot. If not a new mani is needed either with a race cat or a decat altogether
