I am writing this not because there is anything wrong with my car. On the contrary. The car is running better than ever. To recap, I diagnosed a no start condition on our 89 240 to a bad aftermarket Programa 556 ECU. Yesterday I replaced it with a 933 ECU from a 91 740 and all is well. 200 miles later and the car returned a stellar 27mpg in mixed driving with 2 people on board! I couldn't be happier. But for the last 9 months since we bought the car and before I replaced that old ECU I was trying to figure out the poor fuel economy and a very rough cold idle. I replaced all the usual suspects:

02 sensor
FPR
cap/rotor/wires/plugs
harmonic balancer
Switched to electric fan
Thermostat
synthetic oils everywhere
fixed very minor vacuum leak
Cleaned EGR, IAC, TB

No matter what I did the best fuel economy I could manage was 19mpg on the highway. The electric fan bumped it up to 21mpg highway, 18 city.
But all along I never bothered to look at the stupid ECU. I can't believe how much of a difference this can make. Over night the car went from 19 to 27MPG (210 miles on 7.8 gallons)! And it idles as smooth as our 960.
So to recap please stay far far away from Programa or any other aftermarket ECU company. If you have one of these in your car GET RID OF IT! There are enough old Volvos in the junkyards to supply all the computing power you need. And if you sell your car, please tell buyer the car has an aftermarket ECU.