Sticking vanes in variable geometry turbos (VGT) were very common on ’03 to ’06 models due to both an inferior turbo design, and a restrictive turbo oil drain tube. The ’03 to ’05 drain tube (left) was known for limiting oil flow to the point where it couldn’t exit the turbo quick enough, resulting in backed up oil sitting and coking rather than lubricating the turbo vanes. The upgraded-style drain tube (right) can be found on ’06 and ’07 engines and can be used to replace ’03-to-’05-style units. Elite Diesel also informed us that ’07-model turbos came with an internal groove that allowed soot and oil to pass through (no buildup as a result), which greatly reduced scenarios where vanes would stick open or closed. The ’03-to-’06-style turbos do not have this internal groove.