[Ecky]

I imagine the engine will run on the VX ECU, but likely not well, because fueling values will be off by ~7%. When it goes lean, it will be 7% leaner, and may miss or even stall whenever lean burn tries to kick in. One way to compensate might be to increase fuel pressure proportionately, or to have the injectors modified.

If you try to use the chipped ECU, you're likely going to have issues getting a good lean burn tune. For one, I don't believe it can read the VX O2 sensor, and the widebands a chipped ECU can use go out of range around ~18:1. VX lean burn is more in the 22-24:1 range. Additionally, the lean burn ECUs use an entirely different table set for lean burn, which is useful because they don't' have to deal with transition zones in the tables, and you can't do this on a chipped ECU. The main headache is ignition timing - if you're running ~24:1 AFR at part throttle, you need something like an additional 20 degrees of ignition timing. The stock ECU will hold lean burn out to ~90% load, but if you put your transition just before WOT, you'll need some clever way to pull timing before it starts pulling fuel, else you'll get crazy amounts of knock. Also, good luck finding a tuner willing to spend a dozen hours on a brake dyno mapping out part throttle ignition timing values.

My thoughts are, either run the chipped ECU, and accept that it won't really lean burn (maybe mildly, but you'll be giving up 3-6mpg) or run the VX ECU and mechanically compensate for the fuel differences.

Biggest thing for aero will be tucking the wheels back into the wells - you'll get a lot more aero drag with dished wheels that stick out anywhere near the fender. I'd take a wild guess and say this could be worth another 3-4mpg. If you can get a set of Insight wheels, they fit, they're light (~11lbs) and they're extremely aero.