Not saying to run out and buy one until you have a way to check it for sure, but I have heard of a bad/dirty maf causing a random misfire too. Maybe try unhooking the connector at the maf, and then starting it. it will struggle at first, but as soon as it realizes there is no maf signal, it may smooth out. In other words, if it runs better with the maf unhooked (after settling), then your maf is likely the culprit. and that's another free & easy type of test.