Reason I ask is because my MX5 is due its MOT in a month or so - it has struggled in the past to get through (on Emissions!). Mechanic says it is due to lack of use over the winter and it's very low mileage per year use.
Anyway, I put some Injector Cleaner in it 2 years ago and it flew through with no problem. However, last year it 'just' made it again (despite me giving it a good run before the test and using injector cleaner in it).
I was in Halfords yesterday and saw some Emissions Reducer stuff, it actually said 'use before MOT' ..... now, is it bollox or does it get your car through by altering the exhaust fumes in some way?