vehicle is a 1997 civic hatch d16y7.
this started when we were driving through town and all of a sudden the car shuttered and started struggling to run. CEL came on and we shut the vehicle off.
pulled codes,
-P0302 Cylinder 2 misfire
-P0304 Cylinder 4 misfire
-P1399 Multiple missfire detected

after looking it over we discovered the exhaust manifold cracked in half through the o2 primary sensor bung. replaced it with a header and it ran exactly the same. there was discoloration in all but the cylinder 2 runner. so i swapped injectors with another set and even replaced the coil thinking it could be a bad coil. after that the vehicle wouldn't start at all, put the original coil and injectors back in and it fired up but ran the same. swapped 3 different sets of spark plugs, gapped at .044". and still the same. reset the ECU and still the same. did a compression test and it's an even 170 across the board.

now it's just tripping the P1399 code.

also it will run perfect if you mash the gas and wait about 2-3 seconds, it will seem to clear up and pulls hard.

i'm stumped as too what's going on, took the coil to NAPA and had them test the original coil, the new one and another one on the shelf. all of which tested out of range across the primary circuit. not sure if this means all of the coils were bad or if the information i have is wrong on how much resistance they should have. the only thing i have yet to check is timing, but it being an interference engine i'm pretty sure the valves would slam into each other and you would notice it on the compression test and it would be a very noisy top end.