Peter:
The Ultra IBEC not only has the opto coupler on the signal lead, but also a 3 stage filter in the power lead paths. The 3 stage filter is a 2nd order common mode filter (that's 2 stages of the 3) and a low pass filter, so it eats up the predominant amount of noise. As good as the new receivers are, it's still a good idea to eliminate as much of the noise in the leads from the CDI as possible.

You don't want to go directly to the battery, just plug it into an aux channel, and it gets power to the CDI just as if it where a servo.

I can't really comment exactly on fuel comparisons between the 160, 170 &175, as I have only run the 170's. But with a 170 CDI, you can get a good 12 to 14 minutes (2 AMA Masters sequences) and burn maybe 14 oz. About 1 oz / minute. I imagine the 175 would be similar.