My 1993 LS V6 (99000 mi) engine has been rough when idle or accelerationg for some time. My mechanic pulled out the codes 17 & 24 (bad right and left O2 sensors) and suggested me to take the car over to the dealership because both O2S came up bad at the same time indicating that I could have a problem on my ECU or something. However, I can't afford a $150 diagnostics from the dealer. I'd like to know if just replacing the to sensors would be enough or if this O2S problem realy mean big bucks to be spent???