as dieseltrain79 said some cars tend to perform differently on the track compared to dyno. do u have any datalogging or
AFR meter etc? gearbox/converter feels alright?
you need to track tune, make a change every pass and see how it responds.
the brother would track tune the Capri every time it went out, i remember one night jetting changes etc netted as much as 4/10's and 5mph difference. would just check the plugs in the deep end and adjust from there.