what they say in the manual is quite true as far as needle clip position, mine has always been on 2nd groove regardless when I had the 97 needle or now the 98 needle. I did try this test for a while, on 2nd clip at a solid run of 80mph got 40mpg, at 65, 70mph 50mpg. went to 1st groove, 80mph now at 45mpg, 65, 70mph no change still 50mpg. Bu did notice that if cruising at 75mph if 1st groove set-up, and wanted to pass, would need to drop to 4th gear. on 2nd groove set-up cruising same 75mph, no need to down shift. for me the additional 5mpg was not worth it to give up the passing capabilities in 5th, so stuck to the 2nd groove set-up.
I did a lot of runs and many many different jetting combo's and afr runs. my cruise mpg test runs were at a minimum 100 to 125 miles holding speed 65, 70mph and no more, and would do a few of them as well to check for consistency. I spent about the 1st six months playing and testing and comparing my mental notes, comparing to the data from
dyna runs as well. yeah, some could say I was a bit anal about it, but it was fun and quite interesting to see how small changes affected performance from the low end to
wot. now I just enjoy the ride.
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.... se ya'll later. 
Good luck with yours buddy!
, arrive and I go pick it up.
