Check the vaccum advance to see if the unit is leaking vaccum.
>I am new to this list and have recently purchased a 1973 MGBGT. Hopefully
>someone can help me sort out an engine miss I am experiencing at highway
>speeds when under load. This miss is severe and is especially prominent
>when I reach about 60 MPH and press on the gas to go faster or if I put it
>in overdrive and accelerate, or if I start up a slight grade. I do not
>experience the miss when the car is not under load.