pulled P0130 and P0128 codes. I had replace spak plugs because one of the cyclinders was misfiring. Should I change to Volvo plugs? Could that throw the O2 sensor? Or is it the coils? any damage if I don't change the t-stat and t-sensor (as the AC and heat seems to work fine)?

 

the coils should be ok, what kind of plugs were you using? you should stick with either oems or NGK iridiums IV...

 

I have a 2001 s40 and use only iridiums or volvo brand. Coils do go bad and had to replace mine at 45,000.