This happened on my miata and I went through all the motions trying to figure out. For six months..It had no set pattern and when I floored the gas it would almost stall out until I let off on and off bucking the whole way. Thought it was water in the gas, ign coil, wires, everything. This type of vehicular "reaction" typically comes from an air flow meter. Mine had a freyed wire that was simply touching a couple of others. I found it myself by getting so frustrated, I decided to take the whole $%5! car apart to find it. 1st choice was the wire harness going to the air flow meter and sure enough..solved the problemo...