Rought idle at startup, Cyl 4,5,6 Misfire Codes

[ozymail01]

I'm a new owner of a 2004 XC90 T6 AWD. Been working out bugs from previous owners neglect but am stumped on this one. Engine has been idling rough at startup for 10-15 seconds then smooths out. Check Engine was on with showing a Cyl 5 misfire code so I replaced all the spark plugs (they were visibly in need of replacement) and the ignition coil on Cyl 5. Code cleared and life was good for 3 days. Then Check Engine light came back with codes for misfire on Cyl 4, 5 & 6. Knowing I just replaced Cyl 5 ignition and plugs, I can't believe that is the issue. Given the problem seems to be on all 3 cyl. on that sid eof the engine, I'm wondering if this is a turbo issue or some other electrical issue feeding that side. Any ideas?

Ozymail

[ozymail01]

Turned out to be a failing head gasket. :-(