EMphaticONE

I have an 00 SI w/vafc, ctr cams, and stock ecu. When I give it full throttle everything works great when it transitions into VTEC. The problem im experiencing is when im in partial throttle in vtec, in-between the hi to low cam changeover. When i floor the car (switching it to high cam), let off on the throttle, then floor it again the car wont respond for a second or two. Could this be due to my untuned VAFC, or possibly my 100,000 mile spark plugs? Does it mean im running lean?