Another thing worth mentioning is that you are at the point at which you become "used to" your car (3 weeks is about right). I remember when I first picked up my CRX from the shop after getting a b16a swapped into it (about 8 years ago). That thing was freaking insane compared to stock, especially with fwd, I could barely keep the thing in my own lane at first. Then about 3 weeks into it I really felt like something was wrong with it. Felt slower and more manageable but it was only the driver that had changed. I even noticed the same sensation with my S. It started feeling slower as I became "used to" it.

 

Remember: VTEC wont engage if the accelerator is not floored at minimun 75% or is not enough oil pressure.


Maybe you are accelerating pressing the pedal softly or trying to keep it in the edge of function (I hope you understand this, sorry for my english)


Also, U can reset the ECU, maybe it helps to the engine accommodating the VTEC point to your "driving details"...