After my restoration (with new carbs and engine rebuild), I took my 1980 Plus 8 (238,000 miles) in for an MOT to check I'd not missed anything vital. I was disappointed that it failed its emissions and took it home to check it all over. Found two plug leads had been put on incorrectly so I was running a Plus 6 with two cylinder petrol vapour emitters! The long time in lay up had perhaps made me forget how good the performance was.
With plug leads correct, I had an MOT pass and improved performance. If only it was normally so simple.