Im going to guess not alot.. Tuning obd0 isnt something alot of people do. And judging by the type of modifications already on the car, I wouldn't peg it for an obd1 conversion..

Simple things like lowering the fuel pressure and feeding pre-warmed air (not cold air) into the engine would lean the mixture out even farther than the factory maps do. Advancing timing would also help for a more efficient burn and more power.