I get this discussion frequently, and here are the facts. As long as there are no mechanical or electrical concerns, running the VXCF4 based strategy make better power than running the VXCF9 strategy with the same tuning
. This means that as long as there isn't an issue with the EBP sensor not reading correctly or some other similar issue, the earlier strategies run better and produce more power. This dyno plot clearly indicates this:
(click on image to enlarge)
This was tested on Mike Friihauf's (Iron Pig) truck last fall using Matt's SLR+ tune and the files were tuned IDENTICALLY, value for value. We see these same results pretty consistently across all model years. Here's a dyno sheet from my 6.0L with a stock VXBC9 vs VXBC6 strategies:
(click on image to enlarge)
To address the other questions about rollbacks...
As to the whole rollback process itself, we started offering it because of the problem with loss of performance and economy due to dealer updates. Truck owners would drive into Ford for a minor service and leave with a completely different running truck, in most cases with both performance and fuel economy in the toilet. Reflashing the FICM offered some improvement, but quite by accident we found that the later ECM reflashes were also a problem and we started offering ECM rollbacks since Ford was obviously not in a position to offer any assistance. We found the VXCF7xx, VXBC7xx, and VXAP1xx based strategies to be the worst offenders with VXCF9xx, VXBC9xx, and VXAP2xx offering some improvement over the prior release.
Due to the nature of some programmers, if you do not change the base strategy in the ECM, the programmer will use parts of the base strategy to build the modified strategy (using differential file data) which is then reprogrammed back into the ECM. This means that if your stock calibration is a VXBC9xx, it will remain as a VXBC9xx when tuning with certain programmers. I know that the Edge, Bully Dog, Sniper, Superchips, Hypertech, and some SCT programmers all function that way. Now, in regards to the custom tuning aspect on the X-Cal, we have seen issues in the past where customer's trucks have been disabled from using a custom strategy that was not in the same base strategy group as the PCM, meaning that if you had a VXCF9xx ECM and you used a VXCF4xx custom strategy, the PCM would become disabled. In the past we've had to recover several PCMs that suffered this condition, and correcting the custom files to match the ECM strategy would fix the problem. Now I don't know if SCT fixed this issue with subsequent updates to the Advantage software or firmware updates in the devices, so I've been going on the basic assumption that the problem still existed. If you're telling me that a tuner has sent you two different series of the same file and you're not having a problem with running either one, then the problem may no longer be a concern and X-Cal owners may not need to have ECM rollbacks. However, owners of other tuners may still need to consider getting rollbacks in order to increase the effectiveness of both their stock tunes as well as their performance tunes.
I hope this clears up any confusion.