Hello Mazda guys!

So I have a 03 Protege5, and I've recently swapped the engine for a 03 MSP engine and had no problems whatsoever until sparkplug no1 broke inside the engine(No damage to the engine). Have anyone experienced this before? if so what was the reason? Thanks in advance. I'm planning to upgrade the fuel pump, have anyone used the walbro 255? Thoughts?