Lean ??

if you have a handheld tuner you should be able to bump up your A/F ratio 3% or 4%

That seems a bit lean all over. Cruise should hold a pretty steady 14.7. On my stock 97, on a WOT run in 2nd or 3rd, it is around 13.5:1 till 3500, then starts dropping to 12.5ish:1 by 5500. Mufflers should make no appriciable difference in AF ratio.
Try cleaning your mass air meter. When they are dirty or coated in oil, they will read low, causing a lean condition.
As for spraying, you can change the jets until you are happy with the AF ratio. If you think it is too lean, then just put a size bigger fuel jet in. You can buy jets in increments of .001 or something, so you can certainly get the AFs where you want while spraying.

yeah that seems rely lean, at WOT 3500-6k, my a/f ratio pretty much flat lines at 11.7