I'd like to know the answer to this, too - neither the FAQ nor the LTA site covers 'temporary importation', though others have told me that it may be possible.
I can see that a local may fall foul of the regulations if they're trying to circumvent the (utterly riduculous...) CoE rules, but if one is trying to import an existing vehicle for personal use on a temporary basis with a guarantee to re-patriate said vehicle upon departure, then surely this must be a different matter.
I can't find anything or anyone to confirm this, though. I fear that the high duties and taxes may well be the only alternative if you're determined to bring a car. As driving (circuits and road) + all things automotive is 'my thing', it's all pretty dismal.
Depressed of Singapore 