Sure, if you are not ever really accelerating, there won't be any noticeable difference between regular and FEAM, but the fuel savings isn't as much in those cases either (at least I haven't noticed as much), especially when the "regular" map is reflashed and actually more efficient than the stock regular (non-FEAM) map.
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What I observed was the opposite. Compared to a reflashed map (I have the SHodaben Mountain flash), eco gave about a 10% improvement in fuel economy- that's a huge. If I were to drive 700 miles, I'd save maybe around $6, enough for a beer when I arrive and instead of having to possibility have to stop four times, I'd definately have to stop no more than three times for fuel; this would allow me to make it to my destination faster. Also, gas (at least here) has been going up a lot (paid $4 a gallon for 91 last month in N. CA). For me, every two tanks using eco is like someone put an extra $6 in my pocket. Five tanks? An extra $30. I don't recall what the mpg the original stock regular programming gave me, but I think on highway slabbing, I'd get around 47mpg with Guhl. I think GUHL and stock would be equal in mpg. So, I think the Shodaben mountain flash gives maybe +2mpg more than the Guhl. I think the only the Guhl programming did was open those flies sooner.
I don't know if you have a lot of riding time done in the middle of bfe where you have long, flat, straight highways with speed limits of 70-90 posted, and gas stations that can be very, very far away, but if you ever do, you'll see what I mean. I lived near highway 50 (and drove it across the state a few times) and there was at least one stretch where there was no gas for 110 miles.