Hi Sydneysud - the Alfasud boxer engine was designed to run on 98 RON leaded fuel, but the alloy cylinder heads require hardened valve seats as a matter of course and this makes the seats less prone to recession when running on unleaded fuel.
There is really no benefit in putting in octane boosting additives if you run on 98 unleaded (I'm guessing you are in the antipodes, where you seem to be able to get 98 unleaded - over here its dropped a point), but it might still be an idea to use an anti-recession additive if you intend to use the car in the manner intended
Sometimes the engine will smoke if its been laid-up for a long period, but boxers can sometimes smoke for other reasons, such as a broken piston ring letting oil through etc.
One strange problem my current engine had was that one of the inlet valves was cracked. This caused considerable smoking from one cylinder bank. It was unusual in that the engine was brand-new, completely unused, but had been in storage for 20 years. Fortunately all the valves are the same for the single carb 1.5 Ti I was scrapping (cracked block), so I replaced the cracked valve and the engine gave up smoking! I still occassionally worry about another of the valves going the same way...
Lauren
