I bought a Gunsons Gastester years ago and it’s been sitting on a garage shelf since then so i decided to test the MGB – just out of interest.
It’s quite long set up time going by the instructions but once purged it i ran the test on warm engine and the result was quite high at over 7%!! ….which is definitely an mot fail.
Over 4.5% on my year motor is a fail – hey ho at least i know!