The originals bosch injector nozzles were made in germany the new ones are made in India and have major quality control issues, some people report failures after 1000miles should go with italian brand nozzles like bosios or monarks, especially if running wvo. Also do not generally need to replace the whole injector just get new nozzles and bring to diesel shop to rebuild. rebuilding requires more than just installing nozzles as shims must be placed within injector to get correct pressure/bar rating, whcih requires different shim sizes and a pop testor. generally injector nozzles are supposed to be replaced every 100k miles from what I have heard and should make a huge improvement with economy and nailing, rough running etc.