The airplane has the EFII System 32 electronic ignition and electronic fuel injection. There are several positives of using a system like this and one serious negative. The system makes for easier starting and better fuel economy. The downside is that the system is electrically dependent, which means the electrical system has to be very robust, and redundant (compared to a traditional system with a mechanical fuel pump and magnetos).
Anyway. I recently had an issue with the engine surging at high speeds. With help from the manufacturer I was able to find the issue (an unreliable) throttle position sensor. During the course of my investigation I began a discussion with two other pilots that have the EFII system (Sam R and Dwight M). They both were excellent resources.
They looked at my engine data and noted that my fuel pressure tended to drop off a bit at high manifold pressures. We discussed the issue and decided that the fuel pressure regulator was the likely cause. Sam suggested that I replace the FPR from EFII with a better one made by Borla. The cost was about $250, but his own testing suggested that the Borla did a much better job of maintaining fuel pressure.
The hardest part of the job was manufacturing the bracket to mount the Borla FPR on the firewall since its layout was different from the original Aeromotive regulator. With some help from Tom at TSFlightlines I got that part figured out and installed the new FPR. It worked perfectly and the log data showed a very clear improvement over the older regulator.
This is the old pressure regulator.
This is the new pressure regulator. Note that I added a 45 degree adaptor to take some of the tension off the host between the regulator and the #5 injector.
I still need to disassemble the old regulator to check for damage since we think the reason it was not maintaining pressure well is because the steel ball in the regulator had spalled the aluminum seat.