misfiring at idle

My 2008 jimny is misfiring on idle, about 6 months ago I replaced the ignition coils and leads and spark plugs and it fixed the issue. Now its come back but this time also with a check engine light, the bottom of the ignition coils seems to be very corroded and burnt considering they are only 6 months old, also the two ignition coils that are bolted in place (cylinder 1 and 3) are completely fine. It seems like 2 and 4 are not connecting properly or clicking in properly. Any help would be appreciated, Thankyou.

Did you use genuine parts or pattern ones only I've had similar issues historically with pattern leads?

no they are not original suzuki parts they are ridex leads, I will try to find some original suzuki leads and try them. Thankyou