I believe the surge Steve and I were experiencing was a result of detonation. At part throttle "closed-loop" the engine would see over 15psi and over 20 degrees of timing with an Air/Fuel of 14.7. That's way too little fuel for those conditions.

I think stacked is a great mod if you're determined to see how fast you can go in the 1/4 without spray, but it's a PITA when the surge hits and your face almost goes through the windshield. I'm sure this can be remedied by retarding the timing, but at that point your decreasing the power when the objective is to increase it.