hmmm... interesting. The PCM probably was pogrammed with the knowledge the WGA has a 4 or 5 pound spring in it, and cycles the solenoid, etc based on this.. the spring mod probably threw that logic off a bit. Maybe afte rrunning it for a while, the PCM will correct itself to accomodate this.
I had the same huge spike when I did the spring mod with the WGA solenoid still in the loop. I now have the WGA solenoid bypassed completely, and run a MBC and the spring mod. No more crazy spikes, it's pretty much a steady 15 psi the entire time. Actually, I take that back.. I was still getting spikes well over 20 psi at first, but I changed the pressure source to the MBC from the turbo (where i originaly had it), to the throttle body (where the TIP line went).. now the spike is gone.
I'm not so big on pushing that 15psi the second i blip the throttle though, as the PCM is probably still running closed loop and keeping it running at a lean 14.7 until it goes WOT
This is will be fixed as soon as i figure out how to get my throttle switch set up!