A 1989 740 will almost certainly have Bosch engine management and the AMM with a part number ending in 016. I have heard of 1989s with Regina engine management, but they must be very rare. If it has a cylindrical ignition coil then it is Bosch. The Regina coil is rectangular.

The simple test for bad AMM is to disconnect the battery and unplug the AMM. If the car runs better with the AMM unplugged (limp home mode) then the AMM is almost certainly bad. Disconnect the battery to plug it back in too or you might turn a good AMM into a bad one. They are very simple to replace and a good used 016 goes anywhere from $30 to $80 on Ebay depending on the reputation of the seller and how much competition you get in the auction. New ones are almost $400. I haven't heard of any good way to repair one yourself and rebuilt ones have a bad reputation.

Your 240 must be an old one if you don't have an AMM at all.