If the above does not help, you adjust the tickover using the Big Brass Screws (BBS) on each of the throttle bodys. To do this properly you will need to use Morgan Carb Tune, Twinmax or similar balancing device. If you have not got access to one of these, adjust each BBS by exact equal amounts turning them just a little, then rechecking the idle. Try the search facility on this website, there is a 'dummies guide' to throttle body balancing which covers the tickover setup.