Subaru's are know for being picky about spark plugs. You should put what the manual calls for exactly. Then report back.
Did it just start happening after plugs?
The other possible issue would be timing when the chain was replaced. Hopefully its not that. If it is still misfiring after replacing the plugs the next step will be logging and looking at the advance the engine management is going to the timing to see if there is an issue there.
Did it just start happening after plugs?
The other possible issue would be timing when the chain was replaced. Hopefully its not that. If it is still misfiring after replacing the plugs the next step will be logging and looking at the advance the engine management is going to the timing to see if there is an issue there.