Carb. Mechanical or vacuum secondaries?

yep. You drive off the front barrels, and they are set up just like a VS front barrels. I don't know why so many attach VS to fuel economy and DP for being race only.
Not putting DP's in the race only category at all, but common sense dictates the frequent use of the secondaries on a DP WILL reduce economy. The VS carb is an excellent choice for a daily driver.