The problem lies in the inability of timing advance processors(TAP) to advance the spark ignition timing accurately. The 8 spark plug setup being the culprit.CVT belt slippage is a consequence of the above. In theory the problem can be easily overcome by sequential injection. Newly available advancers may also be able to achieve this feat.
I am assuming they wont be backing their claims by any bank guarantee's so the least you can do is do some research about the set up they are using, ie SIS or efi fumigation(with or w/o lambda) and the type, brand of advancer. TAP candidates which i hear are suitable for vario include MAP II by diel and Landirenzo stap 78. There may be others which also work fine so do some research.