P0302 Code Has Me Puzzled

Hey guys. New to the site and to Stangs. I had a 07 Crown Vic P71, which is similar drivetrain wise so I am somewhat familiar with them.

I got this Mustang this last weekend. There was no CEL or anything. I heard a small misfire/stumble when I was checking the car out but didn't think too much about it. Car still goes down the road smooth and seems to have plenty of power/acceleration. It only seems to stumble at idle. I checked out the #2 cylinder and he had a no brand COP on it. I swapped that out with a new OEM and changed all the spark plugs. Once I did that the car seemed to idle a lot better..but not perfect.

Cleared the code and drove it a couple days without the code. Stopped to pick my daughter up today and as I was waiting I felt the car idle a little different. Still no CEL but I checked my codes and sure enough I get the P0302 again.

I did notice when I did the coil that there is a injector that's different then the rest. It isn't OEM, pink in color and it has a different non OEM harness spliced in. It still looks like a EV1 connector just a different style of locking device. I think I will try swapping this out and finding a stock harness and a wrecking yard to splice back in to the harness.

Is there anything else I could check as I am troubleshooting this? I didnt notice any vacuum leaks anywhere, but don't know where actually to look that could cause this.

Thanks for any info given in advance .

Anyone have any type of input? I swapped out the pink injector tonight. Looks like it was some cheap China made Injector. The bottom oring could be moved up and down the lower injector body with the little spacer that was on there too, figured that might have been the culprit. Took the car for a spin to get gas..still can hear a misfire (at least I think, I'm a little paranoid now). Cleared the codes, won't know anything until it picks it back up again, crossing my fingers it doesn't.

Worse case scenario, kind compression throw that misfire code? I am really hoping I don't have to tear into this motor or find a replacement but if I do, I do.

I'll be doing a compression test this weekend. Yeah I was thinking the same thing too about the coil and injector. I know the coils were prone to going out or having a bad one over time. Had happened on a few of the Crown Vics I had owned.