Real world value streams differ not only in their current standard of performance, but also in the most effective actions required to move that particular enterprise towards world class supply. In this paper a generic approach to re-engineering based on the Uncertainty Circle Principle is presented. This has its origin in control engineering with the value stream regarded as subject to four major areas of uncertainty which all affect the ability of the enterprise to deliver. These areas are (Value Added) Process; Supplier; Demand; and Controls Uncertainty. The paper includes examples of good and bad industrial practice observed in real world automotive value streams and shows how these practices can be used to establish a generic change model. For any given business these uncertainties may be codified via the Quick Scan audit procedure. Codification enables critical areas of uncertainty to be pinpointed both for immediate quick-hits and longer-term re-engineering programs based around the well established Material Flow Principles. In the paper the Uncertainty Circle has been used to codify a sample of European automotive sector value steams. The output is a clear portrayal of the present health status of those value streams and identifies specific weaknesses in particular enterprises. The conclusion is that about 10% of our sample are performing at the present day level of best practice, with a further 20% within sight of this goal. Clearly the latter have different re-engineering needs from those enterprises within the sample who so far have failed to achieve internal process control or moved from there to a status of lean production.