Found on the mg-cars.net website now called BBS at https://www.mg-cars.org.uk/
Makes you wonder with the second option just to unscrew the caps and see if they rise together when the engine is revved slightly?
Might give it a try.
To read the full discussion see http://mg-cars.net/mgb-technical-bbs/tuning-with-a-colourtune-2005092422590111787.htm
