MIL light on.
 

So I keep getting a P0301 and a P2187 code. Looking for places to check. I've replaced the MAF sensor, spark plugs, ignition coils. Tested the purge valve. Tried swapping injectors 1&4 and the misfire didn't move.
2187- lean at idle
0301- misfire on cylinder 1
Car is a 2004 Mazda3 2.3l. Has about 170k

Check for a vacuum leak in the inlet manifold where it meets the head at number 1 cylinder. Get a meter or so of windscreen washer sized tubing and stick one end in your ear while moving the other end around the inlet manifold (at idle engine hot an engine cold) listening for the sucking air sound of a vacuum leak.