[djjjr42]

Cool. The flat spot is caused by transitioning from the idle circuit to the main. You should be able to tune that out though. If you're sure that you're rich down low, you need smaller idle jets not bigger ones. However iirc I think my 3 sets of idles are 55,60,and 65 and you said you've got 50. Like I said without a wide band it's really pretty much a lot of trial and error. There is an old-school method of reading your spark plugs, but the procedure is like drive 60mph, immediately pull over and pull the plugs out, lol. Another tip, make sure you keep a log of the different combinations and your observations of each.
Oh yeah, I haven't seen that guide before, cool that you found it.