It wont do any more in a new car than an old car. The diff is, u have to adjust the old one manualy. Either way, if they run high compression they need it, if they dont then they dont.
On a side note, heres somthing u should know about our beloved Optimax. The main diff in this particular 98 fuel is it is high density, which really means u get more fuel per unit and it will last longer IF its leaned out. On a computer equipped car, it compensates by leaning out the fuel mixture automaticly. But with carbies, it will run rich unless u lean it out. Likewise if your already adjusted to Optimax and run any other fuel, u will be lean.
Adam