Guys, by the sounds of it it doesn't happen with the ebc turned off so I don't think it has anything to do with the mechanical setup.
To me, it sounds like poor ebc setup.
I run two of these ebc's with no dramas but if they aren't set up correctly then it can be very discouraging.
Basically, you use the SETGAIN value to bring the boost on earlier. Each individual (mechanical) setup will determine how close you can have your SETGAIN value to your SET value (target boost). For example, my skyline with underturbo'd RB30DET (25 turbo so comes on boost really hard and fast) has a fair difference between the SET and SETGAIN values. My stagea with a stock neo engine and hiflow'd turbo is much lazier coming on boost so I am able to bring the SETGAIN value up closer to the SET value.
Read the manual, the GAIN value can be used to smooth out spiking OR tapering.
First step, is back off the SETGAIN value (even back it off completely) and see if it still spikes after changes.