B5.s4.00'

So I have recently replaced my motor old one lost all compression in cyl 2, after replacing it the cars been running great then just recently it started misfiring in cyl 4 when under load I replaced the coil pack and spark plug because I know this car loves to eat spark plugs, 2.0 coil pack conversion has been done along with stage 2 tuning and emissions deleted, the only thing I can think of is a bad injector any ideas?

I placed a picture of the spark plug I pulled out of the cylinder I know they say your spark plugs can tell a story which only thing I can think of is it running lean.