P0300 Chevrolet - impala 3.4

Question

p0300 Multiple misfire .. have changed coils, plugs and wires, crank and cam sensor, egr valve, o2 sensor bank 1, this started all at once, could it be the timing

Answer 1

P0300 Random misfire
The important part of a random misfire even is the freeze frame when the code is set, If you set this at idle you would need to rule out a mechanical condition such as a cylinder valve problem  by doing a cylinder leakdown test