Ihave to start off by saying that this is a guess because I have not experience with how the electronic ignition works on our gas engines.. It is the old; I am not a doctor, but I play one on TV. Ido have experience with cars. If it popped but did not keep running, it sounds like a timing problem. I wonder if the wheel that has the magnet for the pickup has slipped. If the wheel is slipped on with a flat spot on the shaft, I am wrong because there wouldn't be any slip. If it is a press fit or by held in place by a woodruf key that was not installed, it might have slipped. If you have another Evo to with which you can compare, see if the ignition fires at the same point in the rotation. You might be able to remove the ignition sensor and see when the trigger passes by. Really such a thing takes a degreed wheel on the crank.

G-Pete has knowledge of how the spark plug is fired. You may PM him if he does not see this thread.