http://www.mustangforums.com/m_1873533/tm.htm

First of all, all SVO's came with big Vane meters. The big VAM is not why it is leaning out. The 84 SVO uses the smaller 30lb. fuel injecors commonly known as "green tops." The LA3 which came on the 88 turbo coupes used the brown top 35lb. injectors. If you don't have the brown tops in it that is why it is sputtering and leaning out. After the swap, it will idle like crap for a few minutes so the computer can "learn" the new settings. If you swapped over the premium switch, which is pin 24, you should run good gas and have that boost control solenoid box disconnected. It is the silver box on the passenger side right above the crinkle hose going into the turbo. It will have a solenoid attached to it with a red and yellow wire. In getting rid of that solenoid, you need to put a manual boost controller in its place. They can be purchased at boostvalve.com or you can get parts at a hardware store and make your own. It's a typical ball bearing and spring device. That will let you increase boost above 11-12 lbs. by placing tension on the spring. Tension on the spring makes it harder to blow air passed it opening the wastegate. The boost stops at 11 psi because the wastegate is fully open letting the air by-pass the turbo and run out the exhaust. All SVO's did have the fuel switch and so did turbo coupes. The LA3 is an excellent computer and a lot of people like them over the "P" series computers because of the performance gains. And simply because that the "PE" computers sometimes sell for over 200 dollars.
What you should do is swap the computer and injectors over. Make sure all of the wires are transferred properly. Get a manual boost controller from boostvalve.com. They are about 40 dollars. Make sure the crinkle hose from the VAM to the turbo has the internal reinforcement spring in it so it doesn't collapse and cause the car to buck. Run premium gas and whenever you do a tune up, use only Motorcraft parts. Bosch Platinum crap is horrible for the turbo 2.3 cars.
Some helpful sites are www.turboford.net and www.svoca.com. They have many pages of tech. articles that will help.