i ment understand EXACTLY how it does it, not just guess

all cars these days have closed loop as standard, any car with a cat and some without, even diesels have it these days

if the ECU has closed loup control, then its just another sensor, just like a air temp/water temp sensor

AFR gauge does not measure exhaust temp !!!, its measures the air/fuel ration ( like a breathaliser for a car )

how do you know you have a narrow band already in the T34 ???, btw lambda sensors all differ from ecu to ecu, you cant just get one from a punto and plug it in the mangement

the wideband AFR gauge is just that, just like a boost gauge, you dont use a narrowband gauge on a turbo car as it dont cover the same range that a turbo car has ON BOOST so will register wrong readings