I replaced all my injectors on my 2004.5 5.9L HO 325HP because the old ones were showing signs they need to be replaced. Immediately after I got it back the mileage started to decrease and it continued to fall until it was at 13 mpg and it was at 18mpg. The injectors were replaced with Bosch OEM injectors. The shop that replaced them claim that it just happens to Cummings sometimes. Anything I can do or is the shop right.