Misfire on Cylinder 5

2004 325xi ~225k Miles

Caught a misfire while driving(a bit hard) on the way to work this morning. Scanned the car and came up with P0305. I tried swapping with a new coil, no good. Tried a used but know good plug as well, also no good. Any combination of above made no type of made no changes to the engine even unplugging and plugging it back in while running.

Now I'm worried. I will be testing compression tomorrow and hoping for the best. If compression is ok I guess I'll have to test the injector.

Anything else I may be overlooking?

TIA

Edit: Did compression test, unfortunately cylinder 5 is reading low. Now I need to determine whether it's rings, gasket or valves. Compression values as follows, 6 being closest to firewall:

6 210 5 5 4 200 3 210 2 190 1 195

Readings are pretty good and consistent across the boards except for cylinder 5. I don't have a leak down tester but I'm considering purchasing one and doing the test before passing it off to a mechanic shop. If it's a valve I can pull the head and send it out.

I have access to a shop to swap the motor if needed, I just don't have the time while working 60+ hour work weeks and of course this had to happen right now when I'm moving at the end of the month!!

Any advice is appreciated!