I have almost 170,000 miles on my baby and I'm in the final stages of troubleshooting a misifre. No codes are present, but a rough idle (misifre) is felt at 1200-1500 rpm and I'm about ready to start replacing injectors. I can buy a single injector and hope that Cyl #7 is the culprit (which is likely since it threw a code previously and is a major PITA for the LMG engine) or I can replace all eight injectors at the same time and eliminate all the injectors as a cause of the problem and stave off any future issues in that area. My dilemma, a single injector is $33, whereas the set of eight are $200 (AC Delco on eBay.) At this stage of the game I'm not sure if a complete injector replacement is a good idea or if the remaining injectors are good for 200,000m plus? I'm sure it's a gamble that the other injectors are 100%, so I'm leaning towards a complete replacement since I can do it myself and it's only an additional $167.00. What do you guys think? Note: I've already replaced plugs and wires, cleaned the MAP, replaced the filter, ran two treaments of Lucas and one direct injection of Seafoam. No codes are present, but there's no doubt that I'm getting a misifre somewhere. It's a mystery as to why the ECM isn't picking up on it.