dpfi-mpfi vtec?

ok if someone were to sell me an si head with all of the intake manifold and all that, with the ecu, is this all i need to make my std vtec equipped? or what else do i need?

Si (D16a6) Head is a non-vtec head so yeah you will need to get a vtec head first. you have a couple of options for vtec head.
D16y8
D16z6
Jdm D15B
But if i were in your position i would just get complete Y8 motor. Can be had for cheap and probably cost about the same and put out more power than D15/Y8 mini me.Just my :2cents:. But if you had A6 block wanting to put vtec head on ,i would do differently.
Also you still Have to convert to MPFI.

oh ok, i thought the si was vtec. if i just swapped the heads from my engine d15b with the si head is there anything better in the si head or are they both the same?

As far as the SOHC VTEC heads go, stock for stock the Z6(92-95 Si/EX) head out flows the Y8(96-00 Si) head due to the fact that the Y8 head is biased towards economy(one port is turned a little to encourage swirl), but ported the Y8 is better than the Z6 because of the greater squish area.