if it takes away fuel at WOT, that would make it run lean, yeah?
*I have no experience to actually give, but I'm happy to share my opinion*
Not necessarily. I've tuned more cars than I can count and it is not terribly uncommon to have them running rich at wide open throttle. Generally emissions testing is concentrated on where the engine is operated the most, part throttle cruising. Since the engine is generally not under a super heavy load in this range they tune them as lean as possible to minimize emissions. At wide open throttle and heavy load situations things can go south in a hurry. A richer burn here will be cooler and will help prevent detonation and is thus "safe." It is fairly well standard practice to tune them a little bit richer than optimal for the purposes of just covering their butts and keeping it safe. So yes taking away fuel will make it leaner, but not necessarily make it TOO lean.
In theory, I think you would be fine running a lower octane with a power commander. Since, like you said, the engine is running a pretty low compression ratio, it may be alright. But like you said, if you're dumping more fuel to compensate, you may end up making less power, and have to burn more fuel to compensate, negating any money you may save from running a lower octane.
This is where there is so much mis-understanding in the world it is not even funny. Some people swear up and down that high octane fuel gives you more power. Although it is true that many performance engines require a higher octane fuel, they do not make the power because of it. The octane rating of a fuel determines how hard it is to detonate. If everything else is equal, a higher octane fuel will burn slightly cooler and make LESS power than a lower octane fuel. So why high octane? High performance engines tend to have higher compression and thus are prone to detonation. Increasing the octane rating to prevent detonation will compensate and usually the increase in power from the compression bump offsets the less volatile fuel. Thus to make the most power, you want to run the LOWEST octane fuel possible for your application.
So what does this mean for us? They tuned it super lean for emissions. At only 9:1 compression there is no way it requires high octane fuel unless it is super lean. So what do we get:
1. We add more fuel at a given throttle position and RPM to cool it down a little bit. This would increase fuel consumption.
2. Because the combustion is now cooler we can run a lower octane fuel, which will explode more violently and provide more power.
3. Because the throttle position X at RPM Y now provides more power than it was, we might be able to run at throttle position X-Z to obtain the same desired power. Less throttle means less fuel, which would decrease fuel consumption.
So the question becomes do the factors that decrease fuel consumption outweigh the factors that increase it? Maybe, maybe not. If they do not, does the money saved on non premium fuel offset the economy difference? Maybe, maybe not.
Fortunately I keep meticulous fuel economy records. I can tell you the MPG on every tank of gas I have ever bought. Armed with this information I should be able to quantify any gains or losses in economy from the power commander.
I'm in the process of doing a similar build to your goals. I currently have the Vance and Hines big shots installed, and will be putting a PC next. Then thunder MFG big air kit.
I'm interested to find out what you discover!
Since you are interested, I will most certainly keep you updated! Because I do not have the money to do it all at once, I will be able to track and compare the following:
Power Commander Only
Power Commander and Exhaust
Power Commander and Exhaust and Intake
That is the order I plan on doing the upgrades because Dynojet has those maps available so at no time should I be running around with something grossly out of tune. Once I get it all done and ride around for a while I will probably take it to a shop and have them dyno tune it to see if they can massage a few extra horses out of it. No two vehicles behave exactly the same, even with the same mods.