Do a search and this topic has come up a lot, but it comes down to this, TBS work pretty good on carbs paired with older vehicle, not so good on newer EFI based vehicles. The intake breathes in, in solid gulps in a very rapid fashion.
TBS would work if the intake and valves stayed open all the time. But the fact that they close disrupts the airflow, Remember, intake and exhaust, "pulse", making things that swirl the air pretty useless because the swirl is distrubed everytime.
What you want, in an ideal world, solid condensed, even better cold, air on every intake. Go with syn oil, your engine will thank you and you'll save money in the long run.