just had the same problem. A friends shop 'tested' the coils and said they 'passed', but it kept happening after the plugs and wire replacement i put in...was extremely intermittent, and seemed to be related to outside temp (happened more often in colder weather...almost never happened all summer)...I then read that a lot of shop tests on coils are pointless, as coils will go into death throws were they work temporarily, flip out, then work again...rather than just going from fine to destroyed in one easy step..........
bought the BA replacements from parts geek for $85 shipped or so...been running perfectly ever since.
from what i've seen with P0300 codes related to EGR problems...its a far more subtle missing. A bad coil results in the car being totally undriveable when it happens. Will barely rev, and will immediately stall when trying to apply load to the engine. EGRs getting stuck or clogged can cause a random cylinder code also, but its often just a single cylinder and for a very brief time (only long enough to trip the code, never leave it flashing like i had)...this is often mixed with 'hot idle' problems, where a hot engine will stall or lump down to 100 rpm off throttle as the EGR is stuck open when it shouldn't be.
the best part though...a bad coil can and usually will screw up the EGR valve haha. The unburned fuel will get plumbed through the EGR system and clog up the EGR valve/solenoid pretty quickly. It can also immediately destroy the primary catalyst by dumping raw gasoline into it, which will catch on fire briefly and weld the entire thing shut. I've seen that on a friends Honda Fit, where a bad short from a botched piggy-back installation fried a coil...and after less than a minute of idling with the miss the primary catalyst was white hot...not good...I lucked out as i have a mazdaspeed header and no longer have a primary catalyst because of it, the secondary being too far away to have the same problem.
so just pointing out for future owners with the infamous P0300...it can be a total b**** to locate whats causing it, but don't mess around with it...most parts to remedy the problem are less than $100...but if you manage to destroy a cat and live in a emission regulated area...you're quickly going to approach $1000+ before your next inspection...
